Toner for developing electrostatic latent image, process for producing the same, and process for forming image

ABSTRACT

A toner for developing an electrostatic latent image, a process for producing the same and a process for forming an image using the same are provided. The toner is produced by a simple production process, with good reproducibility, particularly in particle size and particle size distribution. The toner is excellent in production stability, with a wide fixing region, and is also excellent in low temperature fixing property, production stability, storage stability of resin particles formed by the aggregation process, and charging property, particularly environmental stability and time-lapse stability. The toner for developing an electrostatic latent image contains a crystalline resin having a melting point as a binder resin, and at least one of an ester compound having an alkyl group having from 6 to 32 carbon atoms and a resin having a contact angle with water that is smaller than that of the crystalline resin.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a toner for developing anelectrostatic latent image that is suitable for forming a high qualityimage by an electrophotographic process, a process for producing thesame, and a process for forming an image.

[0003] 2. Description of the Related Art

[0004] A process for visualizing image information through anelectrostatic latent image is being widely applied to various fields. Inthe electrophotographic process, an electrostatic latent image is formedon a photoreceptor through a charging step and an exposing step, and theelectrostatic latent image is visualized through a developing step, atransferring step and a fixing step.

[0005] In the electrophotographic process, an electrostatic latent imageformed on a photoreceptor through a charging step and an exposing stepis developed with a developer and then transferred. The toner on afixing material through the transferring step is heated and melted by afixing member having a heating unit in the fixing step, whereby thetoner image is fixed on the surface of the fixing material. In thefixing step, the fixing member heats not only the toner but also thefixing material to the necessary temperature, so as to fix the toner onthe fixing material. When the heating of the fixing material isinsufficient, so-called cold offset occurs, in which only the toner ismelted, and the toner is adhered on the fixing member. When the heatingis excessive, so-called hot offset occurs, in which the viscosity of thetoner is decreased, and a part or the whole of the fixed image isadhered on the fixing member. Therefore, the heating by the fixingmember necessarily falls within a fixing region, in which the coldoffset and the hot offset do not occur.

[0006] According to an increasing demand for energy saving, the fixingtemperature of the toner is necessarily decreased in order to realizeenergy saving of the fixing step, which consumes a certain extent of theconsumed electric power of a duplicator, and enhancement of the fixingregion. The decrease in the fixing temperature of the toner not onlyrealizes the energy saving and the enhancement of the fixing region, butalso shortens the so-called warm-up time, i.e., the latency time untilthe surface of a fixing roll reaches the temperature capable ofconducting fixing upon turning on a duplicator, and enhances the servicelife of the fixing roll.

[0007] When the fixing temperature of the toner is lowered, it bringsabout decrease of the glass transition point of the toner to cause sucha problem that the storage stability of the toner is deteriorated, andthus both the properties cannot be attained at the same time. In orderto realize both the low fixing temperature and the storage stability ofthe toner, it is necessary that the toner has the so-called sharp meltproperty, i.e., the viscosity of the toner is quickly lowered at a hightemperature region while the glass transition point of the toner ismaintained at a high temperature.

[0008] However, because a resin used in the toner generally hasfluctuation ranges in the glass transition point and the molecularweight, it is necessary that the composition and the molecular weight ofthe resin are uniformed to obtain the sharp melt property. In order toobtain such a resin, the molecular weight of the resin is necessarilyuniformed by employing a special production process or by treating theresin with chromatography, whereby the production cost of the resin isconsiderably increased. Furthermore, it is not preferred from thestandpoint of environmental protection since an unnecessary portion ofthe resin is formed.

[0009] As a method for lowering the fixing temperature of the toner, theuse of a crystalline resin as the binder resin is proposed (as describedin Japanese Patent Laid-Open Nos. 129867/1987, 170971/1987, 170972/1987,205365/1987, 276565/1987, 276566/1987, 38949/1988, 38950/1988,38951/1988, 38952/1988, 38953/1988, 38954/1988, 38955/1988, 38956/1988,1217/1993, 148936/1994, 194874/1994, 5056/1993 and 112715/1993).

[0010] Although the fixing temperature can be lowered by these methods,since the gradient of the viscosity of the resin with respect to thetemperature change is large, the sufficient viscosity cannot be obtainedupon production of the toner, for example, upon kneading, and thus thedispersibility of a colorant and a releasing agent in the resin is notstabilized, whereby such a problem occurs that a toner having unevennessin the coloring property and the fixing property is liable to occur.Furthermore, pulverization of the kneaded product becomes difficult tocause such a problem that a toner having a small particle diameter isdifficult to be obtained.

[0011] In order solve the problems, a method can be employed in that anauxiliary agent, such as a thickening agent and a pulverizing aid, isadded, but is not preferred since these auxiliary agents are dispersedin the resin to deteriorate the crystallinity of the binder resin.

[0012] In recent years, an aggregation and coalescence process isproposed as a process for producing a toner, the particle shape or thesurface composition of which is controlled according to the purpose(Japanese Patent Laid-Open Nos. 282752/1988 and 250439/1994). Theaggregation and coalescence process is conducted in the followingmanner. A resin particle dispersion is produced by an emulsionpolymerization process or a dispersion emulsification process, andseparately, a colorant dispersion having a colorant dispersed in asolvent is produced. The dispersions are mixed to form aggregatedparticles having a diameter corresponding to a toner particle diameterand then subjected to heating and fusing to obtain toner particles.According to the aggregation and coalescence process, the toner shapecan be arbitrarily controlled from an irregular shape to a sphericalshape by selecting the conditions for heating temperatures.

[0013] It is general in the aggregation process that the resin particlesare heated to a temperature near the glass transition temperature topartially melt the surface of the resin particles, whereby theaggregated particles are easily produced, and the crystalline resin canbe subjected to the formation of aggregated particles. However, becausethe surface of the crystalline resin particles suffers great change inviscosity particularly near the melting point, the temperature range,within which the surface of the resin particles can be partially melted,is narrow in comparison to an ordinary noncrystalline resin. Thus, inthe case where the aggregation temperature is low, the aggregatedparticles are unstable and easily broken, and in the case where theaggregation temperature is high, the particles are easily grown to causea problem in that the controllability in particle size is deteriorated.In the case of the aggregation process using the crystalline resin, itis necessary to obtain emulsified particles that some kind of adispersant or a hydrophilic functional group is contained in the resin,and it is not preferred since the crystallinity of the resin isdeteriorated.

SUMMARY OF THE INVENTION

[0014] The invention has been made in view of the foregoingcircumstances to solve the problems associated with the conventionaltoner, particularly a full color toner, for developing an electrostaticlatent image, and is to provide:

[0015] (1) A toner for developing an electrostatic latent image and adeveloper for developing an electrostatic latent image that has a widefixing temperature range and are excellent in fixing property at a lowtemperature;

[0016] (2) A toner for developing an electrostatic latent image and adeveloper for developing an electrostatic latent image that areexcellent in charging property, particularly in environmental stabilityand time-lapse stability;

[0017] (3) A toner for developing an electrostatic latent image and adeveloper for developing an electrostatic latent image that can beeasily produced, and are excellent in reproducibility of the particleshape and the particle size distribution and excellent in productionstability;

[0018] (4) A toner for developing an electrostatic latent image and adeveloper for developing an electrostatic latent image that areexcellent in production stability and storage stability of the binderresin particles;

[0019] (5) A process for producing the toner for developing anelectrostatic latent image in a stable manner;

[0020] (6) A process for enabling stable formation of an image by usingthe toner for developing an electrostatic latent image; and

[0021] (7) An apparatus for enabling stable formation of an image byusing the toner for developing an electrostatic latent image.

[0022] According to an aspect of the invention, the toner for developingan electrostatic latent image contains a crystalline resin having amelting point as a binder resin, and the toner further contains at leastone compound which is selected from (a) an ester compound having analkyl group having from 6 to 32 carbon atoms and (b) a resin having acontact angle with water that is smaller than that of the crystallineresin.

[0023] According to another aspect of the invention, the process forproducing a toner for developing an electrostatic latent image containsthe steps of: mixing by agitating a binder resin particle dispersion andan aggregated particle stabilizer dispersion to prepare an aggregatedparticle dispersion containing the binder resin particles; and heatingthe aggregated particle dispersion to a temperature higher than amelting point of a crystalline resin contained in the binder resin toform toner particles.

[0024] According to a further aspect of the invention, a process forforming an image contains the steps of: forming an electrostatic latentimage; developing the electrostatic latent image with a developer toform a toner image; transferring the toner image to a fixing substrate;and fixing the toner image to the fixing substrate. In the process, thetoner for developing an electrostatic latent image described in theabove aspect is used to form the toner image.

BRIEF DESCRIPTION OF THE DRAWING

[0025] A preferred embodiment of the invention will be described indetail based on the following figure, wherein:

[0026]FIG. 1 is a conceptual diagram showing an example of an apparatusfor forming an image for conducting the process for forming an imageaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In the invention, the toner contains a crystalline resin having amelting point as a binding resin and further contains at least one of anester compound having an alkyl group having from 6 to 32 carbon atomsand a resin having a contact angle with water that is smaller than thatof the crystalline resin, whereby it is succeeded that the stability ofthe aggregated particles in the dispersion is ensured, and thecrystallinity of the binder resin is maintained. The stability of theaggregated particles greatly improves dispersibility of a colorant and areleasing agent in the binder resin upon production of the toner by theaggregation and coalescence process, and the maintenance of thecrystallinity of the binder resin enables maintenance of low temperaturefixing property, whereby a toner for developing an electrostatic latentimage that is excellent in low temperature fixing property and colordeveloping property can be provided.

[0028] In general, a crystalline resin suffers great decrease inviscosity at a particular temperature because it has a melting point,and the temperature difference from the start of thermal activity of theresin molecules to the temperature range where fixing can be conductedcan be decreased, whereby an excellent fixing property can be provided.On the other hand, a noncrystalline resin suffers gradual decrease inviscosity to provide a large temperature difference from the start ofthermal activity of the resin molecules at the glass transition point tothe temperature where fixing property can be conducted, and thereforethe low temperature fixing property cannot be ensured.

[0029] According to the invention, the use of the crystalline resinhaving a melting point is enabled to ensure an excellent low temperaturefixing property.

[0030] A crystalline resin having a melting point in a range of from 45to 110° C. is suitable as the crystalline resin of the invention toensure the low temperature fixing property and the storage stability ofthe toner. When the melting point is lower than 45° C., storage of thetoner becomes difficult, and when the melting point exceeds 110° C., theeffect of the low temperature fixing property cannot be enjoyed. Themelting point of the crystalline resin is preferably in a range of from50 to 100° C., and more preferably in a range of from 55 to 90° C. Themelting point of the resin mentioned above was obtained by the processshown in JIS K-7121.

[0031] It is advantageous that the toner of the invention has a smallparticle diameter and a narrow particle size distribution, and issuitably produced by an aggregation and coalescence process, in whichresin particles and colorant particles are aggregated and coalesced. Inthe production of the aggregated particles in this process, it isconsidered that the resin particles and colorant particles dispersed andemulsified to a submicron size exhibiting the Brownian motion formaggregated particles having a diameter of about from 1 to 2 μm due tothe presence of an aggregating agent, i.e., the so-called thermal motionaggregation occurs, and furthermore, the aggregated particles arefurther aggregated to adjust the particle size by heating the aggregatedparticle dispersion, i.e., the so-called flow transportation aggregationoccurs.

[0032] Because the thermal motion aggregation and the flowtransportation aggregation do not simultaneously occur, it is necessaryto stably produce the aggregated particles having a diameter of aboutfrom 1 to 2 μm in order to finally obtain particles having a narrowparticle size distribution. When the aggregation in the flowtransportation aggregation region occurs before sufficiently proceedingthe thermal motion aggregation, the aggregation proceeds with fineparticles remaining, and thus it is not preferred since the particlesize distribution of the toner is broadened.

[0033] The crystalline resin of the invention is hard to be affected bythe temperature below the melting point since a part or the whole of theresin molecules is regularly arranged. Therefore, there is a tendencythat the stability of the aggregated particles having a diameter ofabout from 1 to 2 μm formed by thermal motion aggregation becomes low.Furthermore, when an emulsifier, such as a surfactant, is used in thestage of emulsification, the stability of the aggregated particles isfurther lowered.

[0034] In the invention, an ester compound having an alkyl group havingfrom 6 to 23 carbon atoms is contained in the toner containing acrystalline resin as a binder resin, so as to ensure the stability ofthe aggregated particles with maintaining the low temperature fixingproperty of the crystalline resin, whereby improving the dispersibilityof a colorant and a releasing agent in the binder resin containing thecrystalline resin. That is, it is considered that the ester compoundcontaining an alkyl group improves the compatibility with the colorantand the releasing agent by slightly dissolving with the crystalline partof the crystalline resin, and the partial breakage of the crystallinityof the crystalline resin improves the stability of the aggregatedparticles formed by thermal motion aggregation, whereby thedispersibility of the colorant and the releasing agent in the binderresin containing the crystalline resin is improved. The improvement inthe dispersibility of the colorant and the releasing agent greatlyimproves the coloring property and the fixing property of the toner.Since the compound contains an alkyl group to have low compatibilitywith the crystalline resin in a molten state, it does not inhibit thecrystallinity of the binder resin in the steps of melting, cooling andintegration, whereby the advantage of the low temperature fixingproperty of the crystalline resin can be enjoyed.

[0035] Furthermore, the combination use of the particular resin (theresin having appropriate hydrophilicity) not only improves thehydrophilicity of the various particles upon aggregation for formingaggregated particles by an aggregation process, but also makes particleshaving high hydrophilicity within the aggregated particles be present onthe surface of the aggregated particles due to the difference of contactangles between the crystalline resin particles and the particular resinparticles, whereby the stability of the aggregated particles isimproved.

[0036] When the toner for developing an electrostatic latent image ofthe invention satisfies the following property: when the temperature ischanged within a temperature range of about from 40 to 110° C., thevalue of the storage elastic modulus (GL) and a loss elastic modulus(GN) have an area which is changed by 10² or more at a temperature of10° C., a necessary viscosity can be obtained at the fixing temperature,and the low temperature fixing property can be ensured. When the tonerdoes not satisfied such a property, the necessary viscosity for fixingcannot be obtained, and thus the fixing temperature should be increased,whereby the low temperature fixing property cannot be obtained. Thestorage elastic modulus (GL) and the loss elastic modulus (GN) are morepreferably changed by 10² or more at a temperature difference of 10° C.within a temperature range of from 60 to 90° C.

[0037] It is preferred that the toner for developing an electrostaticlatent image of the invention satisfies the following equation (1):

0≦|log GL(Tm+20)−log GL(Tm+50)|≦1.5  (1)

[0038] wherein Tm represents a melting point, GL(Tm+20) represents astorage elastic modulus at Tm+20° C., and GL(Tm+50) represents a storageelastic modulus at Tm+50° C. It is also preferred that the toner of theinvention satisfies the following equation (2):

0≦|log GN(Tm+20)−log GN(Tm+50)|≦1.5  (2)

[0039] wherein GN(Tm+20) represents a loss elastic modulus at Tm+20° C.,and GN(Tm+50) represents a loss elastic modulus at Tm+50° C. In theforegoing equations, when the value exceeds 1.5, it is not preferredsince hot offset is liable to occur upon high temperature fixing due tolarge dependence on the fixing temperature.

[0040] When the toner for developing an electrostatic latent image ofthe invention has a loss tangent tan δ at Tm+20° C., where Tm representsthe melting point of the toner, satisfying 0.01≦tan δ≦2 at an angularfrequency of 1 rad/sec, excessive penetration into a fixing substrate,such as paper, can be prevented, and simultaneously, the temperatureregion where fixing can be conducted can be broadened. The loss tangenttan δ preferably satisfies 0.1≦tan δ<1.8.

[0041] The crystalline resin used as the binder resin in the inventionis not particularly limited in species as far as it has a melting pointin a range of from 45 to 110° C. The melting point of the crystallineresin is preferably in a range of from 50 to 100° C., and morepreferably in a range of from 55 to 90° C. It is preferred that thetoner containing the binder resin of the invention contains such acrystalline resin that can satisfy the following property: when thetemperature is changed within a temperature range of about from 40 to110° C., the value of the storage elastic modulus (GL) and a losselastic modulus (GN) have an area which is changed by 10² or more at atemperature of 10° C. The storage elastic modulus (GL) and the losselastic modulus (GN) are more preferably changed by 10² or more at atemperature difference of 10° C. within a temperature range of from 60to 90° C.

[0042] A monomer constituting the crystalline resin of the invention isnot particularly limited, and specific examples thereof include vinylseries resins using the following monomers:

[0043] (1) A dicarboxylic acid having a long-chain alkyl group, such asadipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid,dodecanoic diacid and tridecanoic diacid;

[0044] (2) A (meth)acrylate having a long-chain alkyl or alkenyl group,such as amyl (meth)acrylate, hexyl (meth)acrylate, heptyl(meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl(meth)acrylate, undecyl (meth)acrylate, tridecyl (meth)acrylate,myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate,oleyl (meth)acrylate and behenyl (meth)acrylate.

[0045] A polyester resin using a diol having a long-chain alkyl oralkenyl group, such as butanediol, pentanediol, hexanediol, heptanediol,octanediol, nonanediol, decanediol and butyl alcohol.

[0046] The crystalline resin of the invention may contain, in additionto the foregoing monomers, a compound containing an alkyl group, analkenyl group and an aromatic ring having a shorter chain for adjustingthe melting point and the molecular weight. Specific examples thereofinclude the following:

[0047] (1) For the case where the monomer is a dicarboxylic acid, analkyl dicarboxylic acid, such as succinic acid, malonic acid and oxalicacid, an aromatic dicarboxylic acid, such as phthalic acid, isophthalicacid, terephthalic acid, homo phthalic acid, 4,4-bibenzoic acid,2,6-naphthalenedicarboxylic acid and 1,4-naphthalenecarboxilic acid; anda nitrogen-containing aromatic dicarboxylic acid, such as dipicolinicacid, dinicotinic acid, quinolinic acid and 2,3-pyrazinedicarboxylicacid;

[0048] (2) For the case where the monomer is a diol, a diol having ashort-chain alkyl group, such as ethylene grycol, propylene grycol; and

[0049] (3) As a vinyl series monomer having a short-chain alkyl group, a(meth)acrylate of a short-chain alkyl or alkenyl, such as methyl(meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate and a butyl(meth)acrylate, a vinyl nitrile, such as acrylonitrile andmethacrylonitrile, a vinyl ether, such as vinyl methyl ether and vinylisobutyl ether, a vinyl ketone, such as vinyl methyl ketone, vinyl ethylketone and vinyl isopropenyl ketone, and an olefin, such as ethylene,propylene, butadiene and isoprene.

[0050] These monomers may be used singly or in combination of two ormore of them.

[0051] Since the crystalline resin is poor in emulsion dispersibility byits nature, an emulsifier, such as a surfactant, is added. The use of anemulsifier is preferably suppressed because the addition of anemulsifier brings about problems of decrease in charge amount of theparticles and prolongation of a washing step for preventing the decreasein charge amount. In the invention, in the case where a sulfonylgroup-containing monomer is mixed upon polymerization of the crystallineresin, the dispersion stability of the aggregated particles can bemaintained even when the use amount of the emulsifier is decreased. Thespecies of the sulfonyl group-containing monomer is not particularlylimited as far as it can be copolymerized. Specific examples thereofinclude, for the case where the resin is a polyester, a dicarboxylicacid compound having a sulfonyl group directly substituted on thearomatic ring, such as sodium sulfonylterephthalate and sodium3-sulfonylisophthalate, and for the case where the resin is a vinylseries resin, a sulfonyl group-substituted aromatic vinyl compound, suchas a styrene derivative having a sulfonyl group at one of the o-, m- andp-positions and a sulfonyl group-containing vinylnaphthalene.

[0052] The crystalline resin particle dispersion in the invention isliable to cause aggregation by thermal motion aggregation. Even thoughthe aggregation can be suppressed by adding a dispersant or anemulsifier, there are problems of decrease in charge amount of theparticles and prolongation of a washing step for preventing the decreasein charge amount as described in the foregoing. The resin particledispersion is preferably stored at a temperature of 40° C. or less, andmore preferably 20° C. or less. When it is stored at a temperatureexceeding 40° C., it is necessary to re-disperse the aggregatedparticles upon dispersion, and therefore it is not preferred since thedispersion uniformity cannot be ensured, and extra energy for agitatingthe aggregated particles becomes necessary.

[0053] A crosslinking agent may be added to the binder resin of theinvention depending on necessity for preventing hot offset upon fixingin a high temperature region. Specific examples of the crosslinkingagent include the following:

[0054] (1) An aromatic polyvinyl compound, such as divinylbenzene anddivinylnaphthalene;

[0055] (2) A polyvinyl ester of an aromatic polyvalent carboxylic acid,such as divinyl phthalate, divinyl isophthalate, divinyl terephthalate,divinyl homophthalate, divinyl or trivinyl trimesate, divinylnaphthalenedicarboxylate and divinyl biphenylcarboxylate;

[0056] (3) A divinyl ester of a nitrogen-containing aromatic compound,such as divinyl pyridinecarboxylate;

[0057] (4) An unsaturated heterocyclic compound, such as pyrrole andthiophene;

[0058] (5) A vinyl ester of a carboxylic acid of an unsaturatedheterocyclic compound, such as vinyl pyromucinate, vinylfurancarboxylate, vinyl pyrrole-2-carboxylate and vinylthiophenecarboxylate;

[0059] (6) A (meth)acrylate of a linear polyhydric alcohol, such asbutanediol methacrylate, hexanediol acrylate, octanediol methacrylate,decanediol acrylate and dodecanediol methacrylate;

[0060] (7) A (meth)acrylate of a branched or substituted polyhydricalcohol, such as neopentyl glycol dimethacrylate and2-hydroxy-1,3-diacryloxypropane;

[0061] (8) Polyethylene glycol di(meth)acrylate and polypropylenepolyethylene glycol di(meth)acrylate; and

[0062] (9) A polyvinyl ester of a polyvalent carboxylic acid, such asdivinyl succinate, divinyl fumarate, vinyl or divinyl maleate, divinyldiglycolate, vinyl or divinyl itaconate, divinyl acetonedicarboxylate,divinyl glutarate, divinyl 3,3′-thiodipropionate, divinyl or trivinyltrans-aconitate, divinyl adipate, divinyl pimelate, divinyl suberate,divinyl azelate, divinyl sebacate, divinyl didodecanate and divinylbrassylate.

[0063] Particularly in the case where the resin is a polyester, such amethod may be employed in that an unsaturated polycarboxylic acid, suchas fumaric acid, maleic acid, itaconic acid and trans-aconitic acid, iscopolymerized in the polyester, and then crosslinking is effected byusing the multiple bond parts in the resin or other vinyl seriescompounds.

[0064] In the invention, these crosslinking agents may be used singly orin combination of two or more of them.

[0065] The crosslinking method may be such a method that the monomer iswith the crosslinking agent to effect crosslinking, or in alternative,such a method that the unsaturated bond parts are left in the resin, andafter polymerizing the resin or after producing the toner, crosslinkingis effected by a crosslinking reaction of the unsaturated bond parts.

[0066] In the case where the binder resin used in the toner of theinvention is polyester, the monomer may be polymerized by condensationpolymerization.

[0067] As a catalyst for condensation polymerization, known compoundsmay be used, and specific examples thereof include titaniumtetrabutoxide, dibutyltin oxide, germanium dioxide, antimony trioxide,tin acetate, zinc acetate and tin disulfide.

[0068] In the case where the binder resin used in the toner of theinvention is a vinyl series resin, the monomer may be polymerized byradical polymerization.

[0069] An initiator for radical polymerization is not particularlylimited as far as it can initiate emulsion polymerization. Specificexamples thereof include the following:

[0070] (1) A peroxide, such as hydrogen peroxide, acetyl peroxide, cumylperoxide, tert-butyl peroxide, propyonyl peroxide, benzoyl peroxide,chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoylperoxide, lauroyl peroxide, ammonium persulfate, sodium persulfate,potassium persulfate, diisopropyl peroxycarbonate, tetralinhydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, tert-butyltriphenylperacetate hydroperoxide, tert-butyl performate, tert-butylperacetate, tert-butyl perbenzoate, tert-butyl phenylperacetate,tert-butyl methoxyperaceate and tert-butyl N-(3-toluyl)percarbamate;

[0071] (2) An azo compound, such as 2,2′-azobispropane,2,2′-dichloro-2,2′-azobispropane, 1,1′-azo(methylethyl) diacetate,2,2′-azobis(2-amidinopropane)hydrochloride,2,2′-azobis(2-amidinopropane) nitrate, 2,2′-azobisisobutane,2,2′-azobisisobutylamide, 2,2′-azobisisobutylonitrile, methyl2,2′-azobis-2-methylpropionate, 2,2′-dichloro-2,2′-azobisbutane,2,2′-azobis-2-methylbutylonitrile, dimethyl 2,2′-azobisisobutylate,1,1′-azobis(sodium 1-methylbutylonitrile-3-sulfonate),2-(4-methylphenylazo)-2-methylmalonodinitrile,4,4′-azobis-4-cyanovaleric acid,3,5-dihydroxymethylphenylazo-2-methylmalonodinitrile,2-(4-boromophenylazo)-2-allylmalononitrile,2,2′-azobis-2-methylvaleronitrile, dimethyl 4,4′-azobis-4-cyanovalarate,2,2′-azobis-2,4-dimethylvaleronitrile, 1,1′-azobiscyclohexanenitrile,2,2′-azobis-2-propylbutylonitrile, 1,1′-azobis-1-chlorophenylethane,1,1′-azobis-1-cyclohexanecarbonitrile,1,1′-azobis-1-cycloheptanenitrile, 1,1′-azobis-1-phenylethane,1,1′-azobiscumene, ethyl 4-nitrophenylazobenzylcyanoacetate,phenylazodiphenylmethane, phenylazotriphenylmethane,4-nitrophenylazotriphenylmethane, 1,1′-azobis-1,2-diphenylethane,poly(bisphenol A-4,4-azobis-4-cyanopentanoate) and poly(tetraethyleneglycol-2,2′-azobisisobutylate); and

[0072] (3) 1,4-Bis(pentaethylene)-2-tetrazene and 1,4-dimethoxycarbonyl-1,4-diphenyl-2-tetrazene.

[0073] The polymerization initiators may also be used as an initiatorfor the crosslinking reaction in the crosslinking step.

[0074] As the colorant used in the toner of the invention, at least onekind selected from a cyan pigment, a magenta pigment and a yellowpigment may be used. The pigments may be used singly or as a mixture oftwo or more pigments of the same series. Two or more pigments ofdifferent series may also be used as a mixture. Specific examples of thecolorant include various pigments, such as Chrome Yellow, Hansa Yellow,Benzidine Yellow, Suren Yellow, Quinoline Yellow, Permanent Orange GTR,Pyrazolone Orange, Vulkan Orange, Watchyoung Red, Permanent Red,Brilliant Carmine 3B, Brilliant Carmine 6B, Du Pont Oil Red, PyrazoloneRed, Lithol Red, Rhodamine B Lake, Lake Red C, Rose Bengal, AnilineBlue, Ultramarine Blue, Calco Oil Blue, Methylen Blue Chloride,Phthalocyanine Blue, Phthalocyanine Green and Malachite Green Oxalate;and various dyes, such as acridine series, xanthene series, azo series,benzoquinone series, azine series, anthraquinone series, dioxane series,thiazine series, azomethine series, indigo series, thoindigo series,phthalocyanine series, aniline black series, polymethine series,triphenylmethane series, diphenylmethane series, thiazole series andxanthene series. A black pigment or a black dye, such as carbon black,may be added to the colorant in such an extent that the transparency isnot impaired.

[0075] A releasing agent may be added to the toner of the inventiondepending on necessity.

[0076] Specific examples of the releasing agent include a low molecularweight polyolefin, such as polyethylene, polypropylene and polybutene; asilicone compound having a softening point upon heating; an aliphaticamide, such as oleic amide, erucic amide, recinoleic amide and stearicamid; vegetable wax, such as carnauba wax, rice wax, candelilla wax,Japan wax and jojoba oil; animal wax, such as yellow beeswax; andmineral and petroleum wax, such as montan wax, ozokerite, ceresin,paraffin wax, microcrystalline wax and Fischer-Tropsch wax. Thereleasing agents may be used singly or in combination of two or more ofthem.

[0077] The addition amount of the releasing agent is preferably in arange of from 0.5 to 50% by weight, more preferably from 1 to 30% byweight, and further preferably from 5 to 15% by weight. When theaddition amount is less than 0.5% by weight, no effect of addition ofthe releasing agent is obtained. When it exceeds 50% by weight, thecharging property is adversely affected, and the toner is liable to bebroken in a developing unit to make the releasing agent be spent to thecarrier, whereby not only adverse effects, such as decrease in charging,occur, but also in the case where a color toner is used, appearance onthe image surface upon fixing is liable to be insufficient, and thusthere is a possibility that the releasing agent remains in the image todeteriorate the transparency.

[0078] The ester compound used in the invention has an alkyl grouphaving from 6 to 32 carbon atoms, and a compound having a molecularweight of about from 200 to 1,500 is suitably used. When the number ofcarbon atoms of the alkyl group is less than 5, the hydrophilicity ofthe ester compound becomes too high to make the ester compound behydrophilic, and it is not dissolved in the crystalline resin. When thenumber of carbon atoms is 33 or more, it cannot migrate in thecrystalline resin, and thus the dispersion stability of the aggregatedparticles cannot be ensured. When the molecular weight of the estercompound is less than 200, the particle size distribution of theaggregated particles is liable to be broadened since it is difficult tobe compatible with the crystalline resin owing to the large differencein viscosity. When the molecular weight exceeds 1,500, an impurity, suchas an isomer, is liable to be mixed in the ester compound, and it is notpreferred since the controllability is decreased. A polymer having alarge number of carbon atoms, such as polyester, is poor in orientationproperty and cannot be exhibit the addition effect of the ester compoundof the invention. A preferred example of the ester compound of theinvention is one having from 10 to 24 carbon atoms and a molecularweight in a range of from 300 to 700.

[0079] Specific examples of the ester compound used in the inventioninclude the following. These compounds may be used singly or incombination of two or more of them.

[0080] (1) An ester of a higher fatty acid and a higher alcohol, such asstearyl stearate and behenyl behenate;

[0081] (2) An ester of a higher fatty acid and a monohydric orpolyhydric lower alcohol, such as butyl stearate, propyl oleate,monostearic glyceride, distearic glyceride and pentaerythritoltetrabehenate;

[0082] (3) An ester of a higher fatty acid and a polyhydric alcohol,such as diethylene glycol monostearate, dipropylene glycol distearate,distearic diglyceride and tetrastearic triglyceride;

[0083] (4) A sorbitan higher fatty acid ester, such as sorbitanmonostearate; and

[0084] (5) A cholesterol higher fatty acid ester, such as cholesterylstearate.

[0085] In the toner for developing an electrostatic latent imageaccording to the invention, the resin having a contact angle with waterthat is smaller than the crystalline resin forms a difference in contactangle with water from the crystalline resin. The difference in contactangle with water between them is preferably about 3° or more, morepreferably 5° or more, further preferably 10° or more, and particularlypreferably 15° or more. In the case where the difference in contactangle with water is less than 3°, there are cases where the aggregationproperty of the crystalline resin is deteriorated upon production of thetoner by the aggregation process.

[0086] The resin having a contact angle with water that is smaller thanthat of the crystalline resin preferably has a contact angle with waterin the range of about from 30 to 120°, more preferably from 50 to 120°,and further preferably from 70 to 120°. When a resin having a contactangle with water of less than 30° is used, the charging property of thetoner is liable to be affected by humidity, and thus there are caseswhere the environmental stability becomes poor. When a binding resinhaving a contact angle with water exceeding 120° is used, the adhesionproperty with paper upon fixing is deteriorated, and thus there arecases where a toner of poor fixing property is obtained. Similarly, thecrystalline resin preferably has a contact angle with water within theranges described in the foregoing.

[0087] The contact angle with water used herein is measured in thefollowing manner. Powder of the resin to be measured is molded underpressure of about 20 ton/cm² for 30 seconds to produce a resin plate.Pure water is placed in a syringe, and a water droplet of a prescribedsize is prepared. The resin plate is slowly lifted up until the resinplate is in contact with the water droplet, and after the contact, theresin plate is then taken down. A contact angle formed between thetangent line at an edge of the droplet and the surface of the resinplate is measured. The measured contact angle is designated as thecontact angle with water referred herein. The measurement of the contactangle can be conducted by using a commercially available contact anglemeter (Type CA-DTA, produced by Kyowa Interface Science Co., Ltd.).

[0088] When the resin having a contact angle with water that is smallerthan that of the crystalline resin is a resin having a glass transitionpoint that is lower than the melting point of the crystalline resin, atoner having good reproducibility is obtained because upon formation ofthe aggregated particles by the aggregation process, the viscosity ofthe particular resin is lowered at a temperature over the glasstransition point to increase the aggregation force among the particles,and thus the stability, the particle size and the particle sizedistribution of the aggregated particles can be easily controlled.

[0089] Specific examples of the resin having a contact angle with waterthat is smaller than that of the crystalline resin include a homopolymeror a copolymer of a styrene compound, such as styrene, parachlorostyreneand α-methylstyrene (a styrene series resin); a homopolymer or acopolymer of an ester having a vinyl group, such as methyl acrylate,ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate,2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propylmethacrylate, lauryl methacrylate and 2-ethylhexyl methacrylate (a vinylseries resin); a homopolymer or a copolymer of a vinyl nitrile, such asacrylonitrile and methacrylonitrile (a vinyl series resin); ahomopolymer or a copolymer of a vinyl ether, such as vinyl methyl etherand vinyl isobutyl ether (a vinyl series resin); a homopolymer or acopolymer of a vinyl ketone, such as vinyl methyl ketone, vinyl ethylketone and vinyl isopropenyl ketone (a vinyl series resin); ahomopolymer or a copolymer of an olefin, such as ethylene, propylene,butadiene and isoprene (an olefin series resin); a non-vinylcondensation resin, such as an epoxy resin, a polyester resin, apolyurethane resin, a polyamide resin, a cellulose resin and a polyetherresin; and a graft polymer of the non-vinyl condensation resin and thevinyl series monomer. The resins may be used singly or in combination oftwo or more of them.

[0090] The proportion of the resin with respect to the crystalline resinis preferably from 1 to 50%, more preferably from 3 to 40%, and furtherpreferably from 5 to 30%. When the proportion is less than 1%, there arecases where the hydrophilicity of the aggregated particles uponproduction of the toner by the aggregation process becomes insufficient,and it is not preferred since the stability is deteriorated. When itexceeds 50%, the effect of the crystalline resin upon fixing isdifficult to be exhibited, and it is not preferred since there are caseswhere the low temperature fixing property is deteriorated.

[0091] In order to obtain high image quality, the volume averageparticle diameter of the toner of the invention is preferably adjustedto the range of from 3 to 10 μm. When it exceeds 10 μm, thereproducibility of thin lines in the developing step becomes poor, andthus the image quality is deteriorated. When it is lower than 3 μm, itis not preferred since the service life of the developer is shortened.The volume average particle diameter of the toner of the invention ismore preferably in the range of from 4 to 7 μm.

[0092] Process for Producing Toner for Developing Electrostatic LatentImage

[0093] The toner for developing an electrostatic latent image accordingto the invention is preferably produced in the following aggregation andcoalescence process. A resin is agitated and dispersed in a dispersionto prepare a resin particle dispersion, or in alternative, a resinparticle dispersion is produced by emulsion polymerization. The resinparticle dispersion is mixed with a dispersion of an aggregated particlestabilizer and dispersions of a pigment and a releasing agent to effecthetero aggregation, and then the crystalline resin is melted tointegrate the particles to obtain toner particles. The colorant may bepreviously contained in the resin particles. This process is preferredfrom the standpoint of obtaining the foregoing effects. The toner fordeveloping an electrostatic latent image according to the invention mayalso be produced by a dissolution and suspension process and asuspension polymerization process.

[0094] The aggregation and coalescence process of the invention containsa step of mixing at least a resin particle dispersion and a dispersionof an aggregated particle stabilizer, as well as, depending onnecessity, a colorant dispersion and a releasing agent dispersion, so asto aggregate resin particles to form aggregated particles, whereby anaggregated particle dispersion is prepared (an aggregating step), and astep of heating the aggregated particles to form toner particles (acoalescing step).

[0095] In the aggregating step, the hetero aggregation is conducted toform the aggregated particles by adding an ionic surfactant having apolarity different from that of the aggregated particles and a compoundhaving a charge of one or more valent, such as a metallic salt, so as tostabilize the aggregated particles and to control the particle size andthe particle size distribution.

[0096] In the coalescing step, the aggregated particles is heated to atemperature higher than the melting point of the crystalline resincontained in the aggregated particles, so as to obtain the tonerparticles.

[0097] The coalesced particles obtained by coalescing in the coalescingstep are present in an aqueous medium in the form of a colored particledispersion. The dispersion is washed to remove the colored particlesfrom the aqueous medium and to remove impurities formed in therespective steps, followed by drying, so as to obtain the tonerparticles.

[0098] In the washing step, acidic or basic washing water is added in anamount of several times the colored particles, and after agitation, asolid content is obtained by filtration. Pure water is added to thesolid content in an amount of several times the solid content, and afteragitation, filtration is conducted. The foregoing operation is repeatedby several times until the pH of the filtrate after filtration becomesabout 7 to obtain the colored particles.

[0099] In the drying step, the colored particles obtained in the washingstep are dried at a temperature below the melting point of the coloredparticles. At this time, depending on necessity, dried air iscirculated, or heating is effected under vacuum.

[0100] In order to stabilize the resin particle dispersion, the colorantdispersion and the releasing agent dispersion used in the invention, theresin particle dispersion of the invention can be used as it is.However, in the case where the colorant dispersion and the releasingagent dispersion are difficult to be dispersed as they are, or in thecase where the stability of the resin particle dispersion is to bemaintained with the lapse of time, a slight amount of a surfactant maybe employed.

[0101] Examples of the surfactant include an anionic surfactant, such asa sulfate series, a sulfonate series, a phosphate series and a soapseries; a cationic surfactant, such as an amine salt type and aquaternary ammonium salt type; and a nonionic surfactant, such as apolyethylene glycol series, an alkylphenol ethylene oxide adduct seriesand a polyhydric alcohol series. Among these, an ionic surfactant ispreferred, and an anionic surfactant and a cationic surfactant are morepreferred.

[0102] In the production process of the toner of the invention, acationic surfactant is advantageous as a surfactant for dispersing thereleasing agent because an anionic surfactant generally has a highdispersion power and is excellent in dispersion of the resin particlesand the colorant.

[0103] A nonionic surfactant is preferably used in combination with theanionic surfactant or the cationic surfactant. The foregoing surfactantsmay be used singly or in combination of two or more of them. Specificexamples of the anionic surfactant include a fatty acid soap, such aspotassium laurate, sodium oleate and sodium castor oil; a sulfate, suchas octyl sulfate, lauryl sulfate, lauryl ether sulfate and nonyl phenylether sulfate; a sulfonate, lauryl sulfonate, dodecylbenzene sulfonate,a sodium alkylnaphthalene sulfonate, e.g., triisopropylnaphthalenesulfonate and dibutylnaphthalene sulfonate, a naphthalene sulfonateformalin condensate, monooctyl sulfosuccinate, dioctyl sulfosuccinate,lauric amide sulfonate and oleic amide sulfonate; a phosphate, such aslauryl phosphate, isopropyl phosphate and nonyl phenyl ether phosphate;a dialkyl sulfosuccinate, such as sodium dioctyl sulfosuccinate; and asulfosuccinate, such as disodium lauryl sulfosuccinate.

[0104] Specific examples of the cationic surfactant include an aminesalt, such as laurylamine hydrochloride, stearylamine hydrochloride,oleylamine acetate, stearylamine acetate and stearylaminopropylamineacetate; and a quaternary ammonium salt, such as lauryltrimethylammoniumchloride, dilauryldimethylammonium chloride, distearylammonium chloride,distearyldimethylammonium chloride, lauryldihydroxyethylmethylammoniumchloride, oleylbispolyoxyethylenemethylammonium chloride,lauroylaminopropyldimethylethylammonium ethosulfate,lauroylaminopropyldimethylhydroxyethylammonium perchlorate,alkylbenzenedimethylammonium chloride and alkyltrimethylammoniumchloride.

[0105] Specific examples of the nonionic surfactant include an alkylether, such as polyoxyethylene octyl ether, polyoxyethylene laurylether, polyoxyethylene stearyl ether and polyoxyethylene oleyl ether; analkyl phenyl ether, such as polyoxyethylene octyl phenyl ether andpolyoxyethylene nonyl phenyl ether; an alkyl ester, such aspolyoxyethylene laurate, polyoxyethylene stearate and polyoxyethyleneoleate; an alkyl amine, such as polyoxyethylene laurylamino ether,polyoxyethylene stearylamino ether, polyoxyethylene oleylamino ether,polyoxyethylene soy bean amino ether and polyoxyethylene beef tallowamino ether; an alkyl amide, such as polyoxyethylene lauric amide,polyoxyethylene stearic amide and polyoxyethylene oleic amide; avegetable oil ether, such as polyoxyethylene castor oil ether andpolyoxyethylene colza oil ether; an alkanol amide, such as lauricdiethanol amide, stearic diethanol amide and oleic diethanol amide; anda sorbitan ester ether, such as polyoxyethylene sorbitan monolaurate,polyoxyethylene sorbitan monoparmitate, polyoxyethylene sorbitanmonostearate and polyoxyethylene sorbitan monooleate.

[0106] The content of the surfactant in the dispersion may be such anextent that does not impair the invention, and is generally a smallamount. Specifically, in the case of the resin particle dispersion, itis suitably in the range of from 0.01 to 1% by weight, preferably from0.02 to 0.5% by weight, and more preferably from 0.1 to 0.2% by weight.When the content of the surfactant is less than 0.01% by weight, thereare cases where aggregation occurs particularly in the case where the pHof the resin particles dispersion is not sufficiently basic.

[0107] The content of the surfactant in the colorant dispersion and thereleasing agent dispersion is suitably in the range of from 0.01 to 10%by weight, preferably from 0.1 to 5% by weight, and more preferably from0.5 to 2% by weight. When the content of the surfactant is less than0.01% by weight, scattering occurs in the stability among the particlesupon aggregation to cause a problem of isolation of particularparticles. When it exceeds 10% by weight, the particle size distributionis broadened, and the particle diameter is difficult to be controlled.Therefore, both the cases are not preferred.

[0108] To the toner of the invention, particles of other components,such as an internal additive, a charge controlling agent, inorganicparticles, organic particles, a lubricant and an abrasive, may be added,in addition to the binder resin, the colorant and the releasing agent,depending on necessity.

[0109] The internal additive may be used as far as it does not impairthe charging property of the toner characteristics, and examples ofwhich include a metal, an alloy and a compound containing a metal, suchas ferrite, magnetite, reduced iron, cobalt, manganese and nickel.

[0110] The charge controlling agent is not particularly limited, and inthe case where it is used in a color toner, colorless or leucocraticones are preferred. Examples thereof include a quaternary ammonium saltcompound, nigrosine series compound, a dye containing a complex ofaluminum, iron or chromium, and a triphenylmethane series pigment.

[0111] Examples of the inorganic particles include all particles thatare ordinarily used as an external additive to the toner surface, suchas silica, titania, calcium carbonate, magnesium carbonate, tricalciumphosphate and cerium oxide.

[0112] Examples of the organic particles include particles that areordinarily used as an external additive to the toner surface, such as avinyl series resin, a polyester resin and a silicone resin. Theinorganic particles and the organic particles may also be used as afluidity assistant and a cleaning assistant.

[0113] Examples of the lubricant include a fatty acid amide, such asethylenebisstearic amide and oleic amide, and fatty acid metallic salt,such as zinc stearate and calcium stearate.

[0114] Examples of the abrasive include silica, alumina and cerium oxidedescribed in the foregoing.

[0115] Upon mixing the binder resin, the colorant and the releasingagent, the content of the colorant in the toner may be 50% by weight orless, and preferably in the range of from 2 to 40% by weight.

[0116] The contents of the other components may be such an extent thatdoes not impair the effect of the invention, and are generally slightamounts. Specifically, it is generally in the range of from 0.01 to 5%by weight, and preferably from 0.5 to 2% by weight.

[0117] An aqueous medium, for example, is used as the dispersion mediumof the resin particle dispersion, the colorant dispersion, the releasingagent dispersion and other component dispersions of the invention.

[0118] Examples of the aqueous medium include water, such as distilledwater and ion exchanged water, and an alcohol. These may be used singlyor in combination of two or more of them.

[0119] In the preparation step of the aggregated particle dispersion inthe invention, it is preferred to add an aggregating agent, so as toaccelerate and stabilize the aggregation of the particles, and to obtainthe aggregated particles having a narrower particle size distribution.

[0120] As the aggregating agent, a compound having one or more valentcharge is preferred, and specific examples thereof include a watersoluble surfactant, such as an ionic surfactant and a nonionicsurfactant; an acid, such as hydrochloric acid, sulfuric acid, nitricacid, acetic acid and oxalic acid; a metallic salt of an inorganic acid,such as magnesium chloride, sodium chloride, aluminum sulfate, calciumsulfate, ammonium sulfate, aluminum nitrate, silver nitrate, coppersulfate and sodium carbonate; a metallic salt of a fatty acid or anaromatic acid, such as sodium acetate, potassium formate, sodiumoxalate, sodium phthalate and potassium salicylate; a metallic salt of aphenol, such as sodium phenolate; a metallic salt of an amino acid; andan inorganic acid salt of a fatty or aromatic amine, such astriethanolamine hydrochlorate and aniline hydrochlorate.

[0121] A metallic salt of an inorganic acid is preferred from thestandpoint of performance and use with consideration of the stability ofthe aggregated particles, the thermal stability and the time-lapsestability of the aggregating agent, and the removal of the aggregatingagent upon washing.

[0122] The addition amount of the aggregating agent may be a smallamount, while depending on the valence number of charge, and may be 3%by weight or less for monovalence, 1% by weight or less for divalence,and 0.5% by weight or less for trivalence. Since it is preferred thatthe amount of the aggregated agent is as small as possible, a compoundhaving a larger valence is preferred.

[0123] The surface area of the toner for developing an electrostaticlatent image according to the invention is not particularly limited, andno problem occurs when it is in the range that is generally used in atoner. Specifically, the surface area measured by the BET method issuitably from 0.5 to 10 m²/g, preferably from 1.0 to 7 m²/g, and morepreferably from 1.2 to 5 m²/g.

[0124] Inorganic particles, such as silica, alumina, titania and calciumcarbonate, and resin particles, such as a vinyl series resin, apolyester resin and silicone resin, may be added to the surface of thetoner for developing an electrostatic latent image according to theinvention by mixing under application of a shearing force in a drystate. The inorganic particles and the resin particles function as afluidity assistant or a cleaning assistant.

[0125] The absolute value of the charge amount of the toner fordeveloping an electrostatic latent image is suitably in the range offrom 10 to 40 μC/g, and preferably from 15 to 35 μC/g. When the absolutevalue of the charge amount is less than 10 μC/g, background stain isliable to occur, and when it exceeds 40 μC/g, decrease in image densityis liable to occur.

[0126] The ratio of the charge amount in the summer season and thecharge amount in the winter season of the toner for developing anelectrostatic latent image is suitably in the range of from 0.5 to 1.5,and preferably from 0.7 to 1.3. When the ratio is outside the range, itis not preferred from the practical standpoint since the environmentaldependency of the toner becomes large to lack the stability in charging.

[0127] Developer for Developing Electrostatic Latent Image

[0128] The developer for developing an electrostatic latent imageaccording to the invention is not particularly limited except that thetoner for developing an electrostatic latent image according to theinvention is contained, and an appropriate component composition may beemployed depending on purpose.

[0129] The developer for developing an electrostatic latent imageaccording to the invention may be prepared as a one-component developerusing the toner for developing an electrostatic latent image solely, oras a two-component developer using the toner and a carrier incombination.

[0130] The carrier is not particularly limited, and the known carriersmay be employed. For example, the known carrier, such as the resincoated carriers described in Japanese Patent Laid-Open Nos.39879/1987and 11461/1981 may be used.

[0131] Specific examples of the carrier include the following resincoated carriers. Examples of core particles of the carrier includeordinary iron powder, and molded particles of ferrite and magnetite, andthe average particle diameter thereof is about from 30 to 200 μm.

[0132] Examples of the resin coated on the core particles include ahomopolymer of a monomer or a copolymer formed from two or moremonomers, such as a styrene compound, such as styrene, p-chlorostyreneand α-methylstyrene, an α-methylene fatty acid monocarboxylate, such asmethyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate,2-ethylhexyl acrylate, methyl methacrylate, n-propyl methacrylate,lauryl methacrylate and 2-ethylhexyl methacrylate, a nitrogen-containingacrylic compound, such as dimethylaminoethyl methacrylate, a vinylnitrile, such as acrylonitrile and methacrylonitrile, a vinylpyridine,such as 2-vinylpyridine and 4-vinylpyridine, a vinyl ether, such asvinyl methyl ether and vinyl isobutyl ether, a vinyl ketone, such asvinyl methyl ketone, vinyl ethyl ketone and vinyl isopropenyl ketone, anolefin, such as ethylene and propylene, and a vinyl seriesfluorine-containing monomer, such as vinylidene fluoride,tetrafluoroethylene and hexafluoropropylene; a silicone, such asmethylsilicone and methylphenylsilicone; a polyester containingbisphenol and glycol; an epoxy resin; a polyurethane resin; a polyamideresin; a cellulose resin; a polyether resin; and a polycarbonate resin.These resins may be used singly or in combination of two or more ofthem. The amount of the coated resin is suitably in the range of from0.1 to 10 parts by weight based on the core particles, and preferablyfrom 0.5 to 3.0 parts by weight.

[0133] In the production of the carrier, a heating kneader, a heatingHenschel mixer and an UM mixer may be used, and a heating fluidizedrolling bed and a heating kiln may also be used depending on the amountof the coating resin.

[0134] The mixing ratio of the toner and the carrier in the developerfor developing an electrostatic latent image is not particularly limitedand may be appropriately selected depending on purpose.

[0135] Process for Forming Image

[0136] The process for forming an image according to the inventioncontains the step of forming an electrostatic latent image, the step offorming a toner image, the transferring step and the fixing step. Therespective steps for forming an image are ordinary processes anddescribed, for example, in Japanese Patent Laid-Open Nos. 40868/1981 and91231/1974, and they can be applied to a known apparatus for forming animage, such as a duplicator and a facsimile machine.

[0137] In the formation of an electrostatic latent image, anelectrostatic latent image is formed on an electrostatic latent imageholding member. In the formation of a toner image, the electrostaticlatent image is developed with a developer layer on a developer holdingmember to form a toner image. The developer layer is not particularlylimited as far as it contains the developer for developing anelectrostatic latent image according to the invention. In thetransferring step, the toner image is transferred to a fixing substrate.In the fixing step, the toner image transferred to the fixing substrateis fixed on the fixing substrate, such as paper by heating with a fixingmember.

[0138] The characteristic features of the process for forming an imageaccording to the invention are that the fixing temperature of a belttype fixing unit and a roll type fixing unit can be low by using thetoner for developing an electrostatic latent image according to theinvention, excellent in low temperature fixing property, so as to enablehigh speed fixing, and an energy saving effect and an effect ofshortening the warm-up time can be obtained. Particularly, in theprocess for forming an image employing a belt type fixing unit havinglow heating performance for fixing, it is advantageous since good imagequality can be obtained without forming background fogging and coldoffset.

[0139] Apparatus for Forming Image

[0140] An example of an apparatus for forming an image according to theinvention is shown in FIG. 1. The apparatus contains a photoreceptordrum 1 having around the same in the rotation direction a chargingdevice 2, an image writing unit 3 , such as laser light, a developingdevice 4, a primary transferring unit 5 and a cleaning unit 6, andtoners of respective colors, i.e., black, yellow, magenta and cyan, areinstalled in developing units 4 ₁ to 4 ₄ of the developing device 4,respectively. An intermediate transfer belt 7, which is in contact withthe surface of the photoreceptor drum 1 and runs between thephotoreceptor drum 1 and the primary transferring unit 5 in thedirection shown by the arrow, is hung by tension rolls 8 a, 8 b and 8 cand a backup roll 9. A bias roll 10 and a belt cleaner 11 are arrangedto face the backup roll 9 and the tension roll 8 a, respectively.

[0141] A part where the primary transferring unit 5 pushes thephotoreceptor drum 1 through the intermediate transfer belt 7 is aprimary transferring part, and a part where the bias roll 10 pushes thebackup roll 9 is a secondary transferring part. A toner image istransferred from the intermediate transfer belt 7 to transfer paper Psupplied from a paper supplying tray 13 to the secondary transferringpart, and then the transfer paper P is transported to and fixed by afixing unit 14 containing a pressure roll 15 having a heater inside anda transfer belt 16. A pressure pad 17 for pushing the transfer belt 16onto the pressure roll 15 and a belt guide 18 are arranged inside thetransfer belt 16.

[0142] The invention will be described in more detail with reference tothe following examples, but the invention is not construed as beinglimited thereto.

[0143] All the “parts” referred below are parts by weight. The averageparticle diameter of the toner is measured by a Coulter Counter (TypeTA2, produced by Beckman Coulter, Inc.). The particle size distributionof the toner, which is represented by GSDv, is a square root of d₅₀/d₁₆,which is obtained by dividing the particle diameter d₅₀, at which theaccumulated volume diameter from the small diameter side becomes 50%, bythe particle diameter d₁₆, at which the accumulated volume diameter fromthe small diameter side becomes 16%. The melting point of the resinconstituting the toner particles is measured by using a differentialscanning calorimeter (DSC-50, produced by Shimadzu Corp.) under thecondition of a temperature increasing rate of 3° C. per minute.

[0144] The tangent loss (tan δ) is measured by using a viscoelasticitymeasuring apparatus (ARES, produced by Rheometric Scientific FE, Inc.)in the following manner. The toner for developing an electrostaticlatent image is molded into a tablet and set between parallel plateshaving a distance of 8 mm, and after setting the normal force at 0,vibration of a frequency of 1 rad/sec is applied thereto. Themeasurement temperature is started at 40° C. and is continued until 200°C. The measurement is conducted with a measurement interval of 120seconds and a temperature increasing rate after starting the measurementof 1° C. per minute. The distortion amount is maintained at a suitablevalue for each measuring temperature during the measurement, so as toappropriately adjust to obtain adequate measurement values. The storageelastic modulus GL and the loss elastic modulus GN are measured in sucha manner that GL and GN with respect to the temperature is monitoredevery two minutes by using the viscoelasticity measuring apparatus(ARES, produced by Rheometric Scientific FE, Inc.). Preparation of ResinParticle Dispersion (1) Sebacic acid 789.0 parts Ethylene glycol 310.5parts Sodium isophthalate-5-sulfonate 199.7 parts Fumaric acid  40.7parts Dibutyl tin  2.0 parts (all produced by Wako Pure ChemicalIndustries, Ltd.)

[0145] The foregoing components are mixed in a flask and heated to 240°C. under reduced pressure to conduct dehydration condensation for 6hours, so as to obtain a resin. After cooling, 150 parts of the resinare put in 850 parts of distilled water and mixed by agitation with ahomogenizer (Ultra-Turrax, produced by IKA Japan Co., Ltd.) underheating to 85° C., followed by cooling to room temperature to obtain aresin particle dispersion (1). The resulting resin particles have amelting point of 71° C. Preparation of Resin Particle Dispersion (2)Succinic acid 769.8 parts Butanediol 450.5 parts Sodiumisophthalate-5-sulfonate 199.7 parts Fumaric acid  40.7 parts Dibutyltin  2.5 parts (all produced by Wako Pure Chemical Industries, Ltd.)

[0146] The foregoing components are subjected to dehydrationcondensation and mixed by agitation under the same conditions as in thepreparation of the resin particle dispersion (1), so as to obtain aresin particle dispersion (2). The resulting resin particles have amelting point of 90° C. Preparation of Resin Particle Dispersion (3)Azelaic acid 734.0 parts Butanediol 450.5 parts Sodiumisophthalate-5-sulfonate 199.7 parts Fumaric acid  40.7 parts Dibutyltin  2.0 parts (all produced by Wako Pure Chemical Industries, Ltd.)

[0147] The foregoing components are subjected to dehydrationcondensation and mixed by agitation under the same conditions as in thepreparation of the resin particle dispersion (1), so as to obtain aresin particle dispersion (3). The resulting resin particles have amelting point of 49° C. Preparation of Resin Particle Dispersion (4)Terephthalic acid 647.8 parts Decanediol 871.5 parts Sodiumisophthalate-5-sulfonate 199.7 parts Fumaric acid  40.7 parts Dibutyltin  2.0 parts (all produced by Wako Pure Chemical Industries, Ltd.)

[0148] The foregoing components are subjected to dehydrationcondensation and mixed by agitation under the same conditions as in thepreparation of the resin particle dispersion (1), so as to obtain aresin particle dispersion (4). The resulting resin particles have amelting point of 86° C. Preparation of Resin Particle Dispersion (5)Sebacic acid 734.0 parts Ethylene glycol 450.5 parts Sodiumisophthalate-5-sulfonate 199.7 parts Fumaric acid  40.7 parts Dibutyltin  2.0 parts (all produced by Wako Pure Chemical Industries, Ltd.)

[0149] The foregoing components are subjected to dehydrationcondensation and mixed by agitation under the same conditions as in thepreparation of the resin particle dispersion (1), so as to obtain aresin particle dispersion (5). The resulting resin particles have amelting point of 70° C. Preparation of Resin Particle Dispersion (6)Styrene 200 parts Stearyl acrylate 800 parts Sodium P-styrene sulfonate 50 parts Dodecylmercaptan  30 parts (all produced by Wako Pure ChemicalIndustries, Ltd.) Decanediol diacrylate  4 parts (produced byShin-Nakamura Chemical Co., Ltd.)

[0150] A solution obtained by mixing and dissolving the foregoingcomponents is dispersed and emulsified in a solution obtained bydissolving 20 parts of an anionic surfactant (Newlex Paste H, producedby NOF Corp.) in 1,300 parts of ion exchanged water in a flask. Thedispersion is slowly mixed over 10 minutes, and 200 parts of ionexchanged water having 20 parts of ammonium persulfate (produced by WakoPure Chemical Industries, Ltd.) dissolved therein is put therein. Afterconducting substitution with nitrogen, the content of the flask isheated over an oil bath until the content reaches 70° C. under stirring,and emulsion polymerization is continued under the same conditions for 6hours. Thereafter, the reaction mixture is cooled to room temperature toobtain a resin particle dispersion (6). The resulting resin particleshave a melting point of 66° C. Preparation of Colorant Dispersion (1)Phthalocyanine pigment 250 parts (PV Fast Blue, produced byDainichiseika Colour & Chemicals Mfg. Co., Ltd.) Anionic surfactant  20parts (Neogen RK, produced by Dai-ichi Kogyo Seiyaku Co., Ltd.) Ionexchanged water 730 parts

[0151] The foregoing components are mixed and dissolved, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), so as to obtain a colorant dispersion (1) having a colorant(phthalocyanine pigment) dispersed therein. Preparation of ColorantDispersion (2) Yellow pigment 200 parts (C.I.PY180, produced by ClariantJapan Co., Ltd.) Anionic surfactant  20 parts (Newlex R, produced by NOFCorp.) Ion exchanged water 780 parts

[0152] The foregoing components are mixed and dissolved, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), so as to obtain a colorant dispersion (2) having a colorant(yellow pigment) dispersed therein. Preparation of Colorant Dispersion(3) Magenta pigment 300 parts (C.I.PR122, produced by DainichiseikaColour & Chemicals Mfg. Co., Ltd.) Anionic surfactant  25 parts (NewlexR, produced by NOF Corp.) Ion exchanged water 675 parts

[0153] The foregoing components are mixed and dissolved, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), so as to obtain a colorant dispersion (3) having a colorant(magenta pigment) dispersed therein. Preparation of Colorant Dispersion(4) Carbon black 230 parts (Regal 330, produced by Cabot Inc.) Anionicsurfactant  25 parts (Newlex R, produced by NOF Corp.) Ion exchangedwater 745 parts

[0154] The foregoing components are mixed and dissolved, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), so as to obtain a colorant dispersion (4) having a colorant(carbon black) dispersed therein. Preparation of Releasing AgentParticle Dispersion Polyethylene wax (molecular weight: 730) 400 parts(Polywax 725, produced by Toyo Petrolite Co., Ltd.) Anionic surfactant20 parts (Newlex R, produced by NOF Corp.) Ion exchanged water 580 parts

[0155] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain a releasing agent particledispersion having releasing agent particle (polyethylene wax) dispersedtherein. The releasing agent particle dispersion is dried, and themeasurement of the softening point of the remaining releasing agentreveals 98° C. Preparation of Ester Compound Particle Dispersion (1)Stearyl stearate 100 parts (Rikemal SL-800, produced by Riken VitaminCo., Ltd.) (Carbon number of alkyl group of ester compound: 17)(Molecular weight: 522) Anionic surfactant 2 parts (Newlex R, producedby NOF Corp.) Ion exchanged water 300 parts

[0156] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (1) having an ester compound particle dispersed therein.Preparation of Ester Compound Particle Dispersion (2) Butyl stearate 100parts (NIKKO LBS, produced by Nikko Chemicals Co., Ltd.) (Carbon numberof alkyl group of ester compound: 17) (Molecular weight: 354) Anionicsurfactant 2 parts (Newlex R, produced by NOF Corp.) Ion exchanged water300 parts

[0157] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (2) having an ester compound particle dispersed therein.Preparation of Ester Compound Particle Dispersion (3) Butyl laurate 100parts (produced by NOF Corp.) (Carbon number of alkyl group of estercompound: 11) (Molecular weight: 256) Anionic surfactant 2 parts (NewlexR, produced by NOF Corp.) Ion exchanged water 300 parts

[0158] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (3) having an ester compound particle dispersed therein.Preparation of Ester Compound Particle Dispersion (4) Glycerinmono/dibehenate 100 parts (Rikemal B-200, produced by Riken Vitamin Co.,Ltd.) (Carbon number of alkyl group of ester compound: 21) (Molecularweight: 617) Anionic surfactant 2 parts (Newlex R, produced by NOFCorp.) Ion exchanged water 300 parts

[0159] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (4) having an ester compound particle dispersed therein.Preparation of Ester Compound Particle Dispersion (5) Sorbitanmonostearate 100 parts (Emalex SPE-100, produced by Nippon Nyukazai Co.,Ltd.) (Carbon number of alkyl group of ester compound: 17) (Molecularweight: 431) Anionic surfactant 2 parts (Newlex R, produced by NOFCorp.) Ion exchanged water 300 parts

[0160] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (5) having an ester compound particle dispersed therein.Preparation of Ester Compound Particle Dispersion (6) Cholesterylstearate 100 parts (produced by Nikko Chemicals Co., Ltd.) (Carbonnumber of alkyl group of ester compound: 17) (Molecular weight: 649)Anionic surfactant 2 parts (Newlex R, produced by NOF Corp.) Ionexchanged water 300 parts

[0161] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (6) having an ester compound particle dispersed therein.Preparation of Ester Compound Particle Dispersion (7) n-Amyl n-valerate100 parts (produced by Wako Pure Chemical Industries, Ltd.) (Carbonnumber of alkyl group of ester compound: 5) (Molecular weight: 172)Anionic surfactant 2 parts (Newlex R, produced by NOF Corp.) Ionexchanged water 300 parts

[0162] The foregoing components are dissolved by mixing, and the mixtureis dispersed by using a homogenizer (Ultra-Turrax, produced by IKACorp.), followed by subjecting to a dispersion treatment by a pressuredischarge type homogenizer, so as to obtain an ester compound particledispersion (7) having an ester compound particle dispersed therein.

[0163] Production Example of Developer for Developing ElectrostaticLatent Image (1)

[0164] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0165] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.2. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 62° C. under stirring.After maintaining at 62° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.8 μm are formed. After further maintainingat 62° C. for 30 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.4 μm are formed.

[0166] (Coalescing Step)

[0167] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.5, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 3 hours.

[0168] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0169] (Evaluation)

[0170] The resulting toner particles have an average particle diameterof 5.2 μm. 1 Part of colloidal silica (R972, produced by Nippon AerosilCo., Ltd.) is mixed with and externally added to 100 parts of the tonerparticles by using a Henschel mixer to obtain a toner for developing anelectrostatic latent image.

[0171] Preparation of Developer for Developing Electrostatic LatentImage

[0172] 100 Parts of ferrite particles (produced by Powder Tech Co.,Ltd., average particle diameter: 50 μm) and 2.5 parts of a methacrylateresin (produced by Mitsubishi Rayon Co., Ltd., molecular weight: 95,000)are placed in a pressure kneader along with 500 parts of toluene, andmixed by stirring at ordinary temperature for 15 minutes. Thereafter,the temperature is increased to 70° C. with mixing under reducedpressure, and after distilling off the toluene and cooling,classification is conducted by using a sieve of 105 μm to produce aferrite carrier (resin coated carrier).

[0173] The ferrite carrier is mixed with the toner for developing anelectrostatic latent image to produce a two-component developer fordeveloping an electrostatic latent image (1) having a tonerconcentration of 7% by weight.

[0174] Production Example of Developer for Developing ElectrostaticLatent Image (2)

[0175] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (2) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0176] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 82° C. under stirring.After maintaining at 82° C. for 90 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 5.6 μm are formed. After further maintainingat 82° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.9 μm are formed.

[0177] (Coalescing Step)

[0178] The aggregated particle dispersion has pH of 2.1. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 6.0, and the mixture is then heated to 97° C. undercontinuous stirring, followed by maintaining for 5 hours.

[0179] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0180] (Evaluation)

[0181] The resulting toner particles have an average particle diameterof 5.7 μm. A developer for developing an electrostatic latent image (2)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0182] Production Example of Developer for Developing ElectrostaticLatent Image (3)

[0183] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (3) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 12 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0184] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 46° C. under stirring.After maintaining at 46° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.4 μm are formed. After farther maintainingat 46° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 4.5 μm are formed.

[0185] (Coalescing Step)

[0186] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.2, and the mixture is then heated to 75° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0187] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0188] (Evaluation)

[0189] The resulting toner particles have an average particle diameterof 4.7 μm. A developer for developing an electrostatic latent image (3)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0190] Production Example of Developer for Developing ElectrostaticLatent Image (4)

[0191] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (4) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0192] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 86° C. under stirring.After maintaining at 86° C. for 80 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 6.2 μm are formed. After further maintainingat 86° C. for 90 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 6.5 μm are formed.

[0193] (Coalescing Step)

[0194] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 6.2, and the mixture is then heated to 95° C. undercontinuous stirring, followed by maintaining for 5 hours.

[0195] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0196] (Evaluation)

[0197] The resulting toner particles have an average particle diameterof 6.6 μm. A developer for developing an electrostatic latent image (4)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0198] Production Example of Developer for Developing ElectrostaticLatent Image (5)

[0199] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (5) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0200] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 70 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 5.5 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.7 μm are formed.

[0201] (Coalescing Step)

[0202] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.5, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 5 hours.

[0203] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0204] (Evaluation)

[0205] The resulting toner particles have an average particle diameterof 5.9 μm. A developer for developing an electrostatic latent image (5)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0206] Production Example of Developer for Developing ElectrostaticLatent Image (6)

[0207] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (6) 1,063 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 8 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 1000 parts

[0208] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 64° C. under stirring.After maintaining at 64° C. for 50 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 5.1 μm are formed. After further maintainingat 64° C. for 40 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.2 μm are formed.

[0209] (Coalescing Step)

[0210] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 7.2, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 6 hours.

[0211] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0212] (Evaluation)

[0213] The resulting toner particles have an average particle diameterof 5.4 μm. A developer for developing an electrostatic latent image (6)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0214] Production Example of Developer for Developing ElectrostaticLatent Image (7)

[0215] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,767 parts Colorant dispersion (2) 117 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 12 parts Aluminum sulfate 7parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 150 parts

[0216] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 64° C. under stirring.After maintaining at 68° C. for 50 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.9 μm are formed. After further maintainingat 68° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.3 μm are formed.

[0217] (Coalescing Step)

[0218] The aggregated particle dispersion has pH of 2.5. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 5.2, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 6 hours.

[0219] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0220] (Evaluation)

[0221] The resulting toner particles have an average particle diameterof 5.5 μm. A developer for developing an electrostatic latent image (7)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0222] Production Example of Developer for Developing ElectrostaticLatent Image (8)

[0223] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,667 parts Colorant dispersion (3) 250 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 7 parts Aluminum sulfate 7parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 120 parts

[0224] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 68° C. under stirring.After maintaining at 68° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.5 μm are formed. After further maintainingat 68° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.0 μm are formed.

[0225] (Coalescing Step)

[0226] The aggregated particle dispersion has pH of 2.4. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 7.2, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 4 hours.

[0227] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0228] (Evaluation)

[0229] The resulting toner particles have an average particle diameterof 5.2 μm. A developer for developing an electrostatic latent image (8)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0230] Production Example of Developer for Developing ElectrostaticLatent Image (9)

[0231] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts Colorant dispersion (4) 109 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0232] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 67° C. under stirring.After maintaining at 67° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.8 μm are formed. After further maintainingat 67° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.0 μm are formed.

[0233] (Coalescing Step)

[0234] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 5.5, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 4 hours.

[0235] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0236] (Evaluation)

[0237] The resulting toner particles have an average particle diameterof 5.2 μm. A developer for developing an electrostatic latent image (9)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0238] Production Example of Developer for Developing ElectrostaticLatent Image (10)

[0239] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (2) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0240] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.9 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.1 μm are formed.

[0241] (Coalescing Step)

[0242] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0243] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0244] (Evaluation)

[0245] The resulting toner particles have an average particle diameterof 5.2 μm. A developer for developing an electrostatic latent image (10)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0246] Production Example of Developer for Developing ElectrostaticLatent Image (11)

[0247] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (3) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0248] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.5 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 4.8 μm are formed.

[0249] (Coalescing Step)

[0250] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0251] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0252] (Evaluation)

[0253] The resulting toner particles have an average particle diameterof 5.0 μm. A developer for developing an electrostatic latent image (11)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0254] Production Example of Developer for Developing ElectrostaticLatent Image (12)

[0255] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (4) 200 parts Lauroyl peroxide 10 parts Aluminum sulfate 5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0256] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.9 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 4.9 μm are formed.

[0257] (Coalescing Step)

[0258] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.1, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0259] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0260] (Evaluation)

[0261] The resulting toner particles have an average particle diameterof 5.1 μm. A developer for developing an electrostatic latent image (12)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0262] Production Example of Developer for Developing ElectrostaticLatent Image (13)

[0263] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts   Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (5) 200 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0264] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.9 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.4 μm are formed.

[0265] (Coalescing Step)

[0266] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 4.8, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0267] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0268] (Evaluation)

[0269] The resulting toner particles have an average particle diameterof 5.7 μm. A developer for developing an electrostatic latent image (13)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0270] Production Example of Developer for Developing ElectrostaticLatent Image (14)

[0271] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts   Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (6) 200 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0272] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 5.0 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.2 μm are formed.

[0273] (Coalescing Step)

[0274] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.2, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0275] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0276] (Evaluation)

[0277] The resulting toner particles have an average particle diameterof 5.3 μm. A developer for developing an electrostatic latent image (14)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0278] Production Example of Developer for Developing ElectrostaticLatent Image (15)

[0279] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts   Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (1) 100 parts Ester compound particle dispersion (6) 100parts Lauroyl peroxide  10 parts Aluminum sulfate  5 parts (produced byWako Pure Chemical Industries, Ltd.) Ion exchanged water 100 parts

[0280] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.8 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.1 μm are formed.

[0281] (Coalescing Step)

[0282] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0283] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0284] (Evaluation)

[0285] The resulting toner particles have an average particle diameterof 5.5 μm. A developer for developing an electrostatic latent image (15)is prepared by using the resulting toner particles in the same manner asin the preparation of the developer for developing an electrostaticlatent image (1).

[0286] Production Example of Developer for Developing ElectrostaticLatent Image (16)

[0287] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts   Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Lauroyl peroxide  10 partsAluminum sulfate  5 parts (produced by Wako Pure Chemical Industries,Ltd.) Ion exchanged water 300 parts

[0288] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.9 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.3 μm are formed.

[0289] (Coalescing Step)

[0290] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0291] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0292] (Evaluation)

[0293] The resulting toner particles have an average particle diameterof 5.5 μm, and the particle size distribution is slightly broad. Adeveloper for developing an electrostatic latent image (16) is preparedby using the resulting toner particles in the same manner as in thepreparation of the developer for developing an electrostatic latentimage (1).

[0294] Production Example of Developer for Developing ElectrostaticLatent Image (17)

[0295] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (1) 2,833 parts   Colorant dispersion (1) 100 partsReleasing agent particle dispersion 125 parts Ester compound particledispersion (7) 100 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 300 parts

[0296] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 60 minutes, the observation by anoptical microscope confirms that aggregated particles having an averageparticle diameter of about 4.8 μm are formed. After further maintainingat 65° C. for 60 minutes, the observation by an optical microscopeconfirms that aggregated particles having an average particle diameterof about 5.1 μm are formed.

[0297] (Coalescing Step)

[0298] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours.

[0299] Thereafter, the reaction product is filtered and sufficientlywashed with ion exchanged water, followed by drying by using a vacuumdryer, so as to obtain toner particles.

[0300] (Evaluation)

[0301] The resulting toner particles have an average particle diameterof 5.3 μm, and the particle size distribution is slightly broad. Adeveloper for developing an electrostatic latent image (17) is preparedby using the resulting toner particles in the same manner as in thepreparation of the developer for developing an electrostatic latentimage (1).

[0302] Preparation of Apparatus for Forming Image (1)

[0303] The fixing unit of a color duplicator, Acolor 930, produced byFuji Xerox Co., Ltd., is detached, from which the releasing oilsupplying unit is then detached, and a fixing unit containing a fixingroll and a pressure roll having films of a ethylene-vinylidenefluoride-tetrafluoroethylene copolymer on the surfaces thereof isinstalled, so as to prepare an apparatus for forming an image (1).

[0304] Preparation of Apparatus for Forming Image (2)

[0305] An apparatus for forming an image (2) is prepared in the samemanner as in the apparatus for forming an image (1) except that a fixingbelt formed with a polyimide film is used instead of the pressure roll.

EXAMPLE 1

[0306] The developer of the production example of a developer fordeveloping an electrostatic latent image (1) is installed in adeveloping unit of the apparatus for forming an image (1), and anon-fixed image is prepared to have a solid part and a thin line part.The non-fixed image is fixed by the fixing unit of the apparatus forforming an image (1) in such a manner that the rotation speed of theroll is adjusted to make the contact time of the fixing roll and thenon-fixed image be 0.04 second, with the surface temperature of thefixing roll varying from 60 to 200° C. at an interval of 5° C. The fixedimage is folded inside at the substantial center of the solid part ofthe fixed image to evaluate the breakage of the fixed image, and thefixing temperature where no problem occurs is designated as the lowestfixing temperature. Reproducibility of the thin lines, backgroundfogging and hot offset are evaluated with the naked eye.

EXAMPLES 2 TO 15

[0307] Fixing is conducted and evaluated in the same manner as inExample 1 except that the developers of the production examples of adeveloper for developing an electrostatic latent image (2) to (15) areused.

EXAMPLE 16

[0308] The developer of the production example of a developer fordeveloping an electrostatic latent image (1) is installed in adeveloping unit of the apparatus for forming an image (2), and anon-fixed image is prepared to have a solid part and a thin line part.The non-fixed image is fixed under the same conditions as in Example 1except that the speed of the belt is adjusted to make the contact timeof the fixing belt of the fixing unit of the apparatus for forming animage (2) and the non-fixed image be 0.08 second. A fixing operation isconducted in the same manner as in Example 1 about other conditions andevaluation is conducted for the image.

Comparative Example 1

[0309] A fixing operation is conducted in the same manner as in Example1 except that the developer of the production example of a developer fordeveloping an electrostatic latent image (16) is used, and evaluation isconducted in the same manner as in Example 1.

Comparative Example 2

[0310] A fixing operation is conducted in the same manner as in Example1 except that the developer for Acolor 936, produced by Fuji Xerox Co.,Ltd. is used, and evaluation is conducted in the same manner as inExample 1.

Comparative Example 3

[0311] A fixing operation is conducted in the same manner as in Example1 except that the developer of the production example of a developer fordeveloping an electrostatic latent image (17) is used, and evaluation isconducted in the same manner as in Example 1.

[0312] Evaluation

[0313] The characteristics of the toners used in Examples 1 to 15 andComparative Examples 1 to 3 are shown in Table 1 below, and the averageparticle diameter, the particle size distribution GSDv and the fixingcharacteristics thereof are shown in Table 2 below. In the tables, Tmrepresents the melting point of the toner, GL(30) represents the storageelastic modulus at 30° C.; GL(Tm) and GL(Tm+10) represent the storageelastic modulus at the melting point and that at a temperature higher by10° C. than the melting point, respectively; GN(Tm) and GN(Tm+10)represent the loss elastic modulus at the melting point and that at atemperature higher by 10° C. than the melting point, respectively; ΔlogGL represents |log GL(Tm+20)−log GL(Tm+50)|; and Δlog GN represents |logGN(Tm+20)−log GN(Tm+50)|. TABLE 1 Tm GL(30) × GL(Tm) × GL(Tm + 10) ×GN(Tm) × GN(Tm + 10) × (° C.) 10⁵ 10⁵ 10³ 10⁵ 10³ Δlog GL Δlog GNExample 1 72 2.1 7.6 5.0 7.4 4.6 1.1 1.2 Example 2 92 5.3 6.5 6.2 6.35.9 1.2 1.0 Example 3 49 1.6 1.8 9.2 1.9 9.0 1.4 1.4 Example 4 88 4.85.4 2.2 5.1 2.3 0.4 0.3 Example 5 70 2.0 8.6 1.5 8.5 1.4 0.6 0.6 Example6 67 1.8 3.2 8.3 3.2 8.2 0.3 0.2 Example 7 71 2.1 7.7 5.2 7.4 4.5 1.01.2 Example 8 72 2.1 7.6 4.8 7.2 4.5 1.0 1.1 Example 9 71 2.1 7.6 5.07.5 4.7 0.9 0.9 Example 10 70 2.1 7.4 4.9 7.4 5.0 1.0 1.1 Example 11 722.1 7.3 4.6 7.2 4.4 0.6 0.5 Example 12 72 2.1 7.0 3.8 6.8 3.6 0.8 0.7Example 13 71 2.1 7.1 5.2 6.8 5.0 1.2 1.3 Example 14 72 2.1 7.4 5.0 7.35.0 1.0 0.8 Example 15 72 2.1 7.1 4.0 6.8 3.6 0.7 0.6 Comparative 73 2.17.2 4.8 7.1 4.5 1.2 1.1 Example 1 Comparative — 1.6 — — — — — — Example2

[0314] TABLE 2 Average Fixing diameter temperature Reproducibility ofBackground (μm) GSDv (° C.) thin lines fogging Hot offset Example 1 5.21.23 85 good none no occurrence Example 2 5.7 1.21 100  good none nooccurrence Example 3 4.7 1.25 60 good none no occurrence Example 4 6.61.26 95 good none no occurrence Example 5 5.9 1.24 80 good none nooccurrence Example 6 5.4 1.22 75 good none no occurrence Example 7 5.51.21 85 good none no occurrence Example 8 5.2 1.25 80 good none nooccurrence Example 9 5.2 1.25 85 good none no occurrence Example 10 5.21.24 85 good none no occurrence Example 11 5.0 1.27 85 good none nooccurrence Example 12 5.1 1.22 85 good none no occurrence Example 13 5.71.24 85 good none no occurrence Example 14 5.3 1.23 85 good none nooccurrence Example 15 5.5 1.22 85 good none no occurrence Example 16 5.21.22 90 good none no occurrence Comparative 5.5 1.35 85 slightly poorslight occurrence no occurrence Example 1 Comparative 7.0 1.34 150 slightly poor slight occurrence occurrence at Example 2 180° C.Comparative 5.3 1.39 85 slightly poor slight occurrence no occurrenceExample 3

[0315] It is understood from Tables 1 and 2 that, in comparison to thedevelopers for developing an electrostatic latent image containing thetoners for developing an electrostatic latent image of ComparativeExamples 1 to 3, the developers for developing an electrostatic latentimage containing the toners for developing an electrostatic latent imageof Examples 1 to 15 have a narrow particle size distribution, i.e., theparticle diameters of the respective particles of the toner can beuniformized, and therefore the toners for developing an electrostaticlatent image can be obtained that are excellent in reproducibility ofthin lines and cause no background fogging. Furthermore, when the samedeveloper for developing an electrostatic latent image containing thetoner for developing an electrostatic latent image as in Example 1 isinstalled in the apparatus for forming an image (2) having a fixingbelt, and the image quality is evaluated, an image that is excellent inreproducibility of thin lines and causes no background fogging can bestably formed as similar to the other Examples.

[0316] Experimental examples of a toner for developing an electrostaticlatent image containing at least one resin having a contact angle withwater that is smaller than the crystalline resin will be describedbelow.

[0317] The contact angle with water of the resin is measured by using acommercially available contact angle meter (Type CA-DTA, produced byKyowa Interface Science Co., Ltd.) in the following manner. Powder ofthe resin to be measured is middle under pressure of about 20 ton/cm2for 30 seconds to produce a resin plate. A water droplet is made incontact with the surface of the resin plate, and the contact angle ismeasured at room temperature. Preparation of Resin Particle Dispersion(7) Sebacic acid 940.7 parts Ethylene glycol 310.5 parts Fumaric acid 40.6 parts Dibutyl tin  2.0 parts (all produced by Wako Pure ChemicalIndustries, Ltd.)

[0318] The foregoing components are mixed in a flask and heated to 240°C. under reduced pressure to conduct dehydration condensation for 6hours, so as to obtain a resin. After cooling, it is found that theresin has a melting point of 72° C. and a contact angle with water of88°. 150 parts of the resin are put in 850 parts of distilled water andmixed by agitation with a homogenizer (Ultra-Turrax, produced by IKAJapan Co., Ltd.) under heating to 85° C., so as to obtain a resinparticle dispersion (7). Preparation of Resin Particle Dispersion (8)Succinic acid 679.4 parts Butanediol 450.5 parts Fumaric acid  40.6parts Dibutyl tin  2.5 parts (all produced by Wako Pure ChemicalIndustries, Ltd.)

[0319] The foregoing components are subjected to dehydrationcondensation under the same conditions as in the resin particledispersion (7) to obtain a resin having a melting point of 91° C. and acontact angle with water of 86°. The resin is then subjected to mixingby agitation under the same conditions as in the resin particledispersion (7) to obtain a resin particle dispersion (8). Preparation ofResin Particle Dispersion (9) Azelaic acid 875.1 parts Butanediol 450.5parts Fumaric acid  40.7 parts Dibutyl tin  2.0 parts (all produced byWako Pure Chemical Industries, Ltd.)

[0320] The foregoing components are subjected to dehydrationcondensation under the same conditions as in the resin particledispersion (7) to obtain a resin having a melting point of 60° C. and acontact angle with water of 89°. The resin is then subjected to mixingby agitation under the same conditions as in the resin particledispersion (7) to obtain a resin particle dispersion (9). Preparation ofResin Particle Dispersion (10) Terephthalic acid 772.4 parts Decanediol871.5 parts Fumaric acid  40.6 parts Dibutyl tin  2.0 parts (allproduced by Wako Pure Chemical Industries, Ltd.)

[0321] The foregoing components are subjected to dehydrationcondensation under the same conditions as in the resin particledispersion (7) to obtain a resin having a melting point of 86° C. and acontact angle with water of 82°. The resin is then subjected to mixingby agitation under the same conditions as in the resin particledispersion (7) to obtain a resin particle dispersion (10). Preparationof Resin Particle Dispersion (11) Sebacic acid 900.2 parts Ethyleneglycol 450.5 parts Sodium isophthalate-5-sulfonate  53.2 parts Fumaricacid  40.6 parts Dibutyl tin  2.0 parts (all produced by Wako PureChemical Industries, Ltd.)

[0322] The foregoing components are subjected to dehydrationcondensation under the same conditions as in the resin particledispersion (7) to obtain a resin having a melting point of 69° C. and acontact angle with water of 89°. The resin is then subjected to mixingby agitation under the same conditions as in the resin particledispersion (7) to obtain a resin particle dispersion (11). Preparationof Resin Particle Dispersion (12) Styrene 300 parts Stearyl acrylate 700parts Dodecylmercaptan  6 parts (all produced by Wako Pure ChemicalIndustries, Ltd.) Decanediol diacrylate  4 parts (produced byShin-Nakamura Chemical Co., Ltd.)

[0323] A solution obtained by mixing and dissolving the foregoingcomponents is dispersed and emulsified in a solution obtained bydissolving 20 parts of an anionic surfactant (Newlex Paste H, producedby NOF Corp.) in 1,300 parts of ion exchanged water in a flask. Thedispersion is slowly mixed over 10 minutes, and 200 parts of ionexchanged water having 20 parts of ammonium persulfate (produced by WakoPure Chemical Industries, Ltd.) dissolved therein are put therein. Afterconducting substitution with nitrogen, the content of the flask isheated over an oil bath until the content reaches 70° C. under stirring,and emulsion polymerization is continued under the same conditions for 6hours. Thereafter, the reaction mixture is cooled to room temperature,followed by washing and drying, so as to obtain a resin particledispersion (12) having a melting point of 61° C. and a contact anglewith water of 82°. Preparation of Resin Particle Dispersion (13) Sebacicacid 738.4 parts Ethylene glycol 310.5 parts Sodiumisophthalate-5-sulfonate 266.2 parts Fumaric acid  40.6 parts Dibutyltin  2.0 parts (all produced by Wako Pure Chemical Industries, Ltd.)

[0324] The foregoing components are subjected to dehydrationcondensation under the same conditions as in the resin particledispersion (7) to obtain a resin having a melting point of 59° C. and acontact angle with water of 79°. The resin is then subjected to mixingby agitation under the same conditions as in the resin particledispersion (7) to obtain a resin particle dispersion (13). Preparationof Resin Particle Dispersion (14) Styrene 300 parts Stearyl acrylate 700parts Acrylic acid  20 parts Dodecylmercaptan  12 parts (all produced byWako Pure Chemical Industries, Ltd.) Decanediol diacrylate  4 parts(produced by Shin-Nakamura Chemical Co., Ltd.)

[0325] A solution obtained by mixing and dissolving the foregoingcomponents is dispersed and emulsified in a solution obtained bydissolving 18 parts of an anionic surfactant (Newlex Paste H, producedby NOF Corp.) in 1,300 parts of ion exchanged water in a flask. Thedispersion is slowly mixed over 10 minutes, and 200 parts of ionexchanged water having 16 parts of ammonium persulfate (produced by WakoPure Chemical Industries, Ltd.) dissolved therein are put therein. Afterconducting substitution with nitrogen, the content of the flask isheated over an oil bath until the content reaches 70° C. under stirring,and emulsion polymerization is continued under the same conditions for 6hours. Thereafter, the reaction mixture is cooled to room temperature toobtain a resin having a melting point of 56° C. and a contact angle withwater of 78°. A resin particle dispersion (14) is prepared from theresultant resin under the same condition as in the resin particledispersion (7).

[0326] Developer for Developing Electrostatic Latent Image (18)

[0327] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 2,400 parts   (contact angle with water: 88°)Resin particle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion  63 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0328] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 68° C. under stirring.After maintaining at 68° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.9 μm are formed. After further maintaining at 68° C.for 1 hour, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.2 μmare formed.

[0329] (Coalescing Step)

[0330] The aggregated particle dispersion has pH of 2.4. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 85° C. undercontinuous stirring, followed by maintaining for 3 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0331] The resulting toner particles have an average particle diameterof 5.3 μm. 1 Part of colloidal silica (R972, produced by Nippon AerosilCo., Ltd.) is externally added to 100 parts of the toner particles,followed by mixing by a Henschel mixer, to obtain a toner for developingan electrostatic latent image.

[0332] Preparation of Developer for Developing Electrostatic LatentImage

[0333] 100 Parts of ferrite particles (produced by Powder Tech Co.,Ltd., average particle diameter: 50 μm) and 3.0 parts of a methacrylateresin (produced by Mitsubishi Rayon Co., Ltd., molecular weight: 95,000)are placed in a pressure kneader along with 500 parts of toluene, andmixed by stirring at ordinary temperature for 15 minutes. Thereafter,the temperature is increased to 70° C. with mixing under reducedpressure, and after distilling off toluene, the content is cooled andclassified by using a sieve of 105 μm to produce a ferrite carrier(resin coated carrier). The ferrite carrier is mixed with the toner fordeveloping an electrostatic latent image to produce a two-componentdeveloper for developing an electrostatic latent image (18) having atoner concentration of 7% by weight.

[0334] Developer for Developing Electrostatic Latent Image (19)

[0335] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (8) 2,400 parts   (contact angle with water: 86°)Resin particle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion  63 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0336] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 84° C. under stirring.After maintaining at 84° C. for 4 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 6.6 μm are formed. After further maintaining at 84° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 6.9 μmare formed.

[0337] (Coalescing Step)

[0338] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 4.8, and the mixture is then heated to 98° C. undercontinuous stirring, followed by maintaining for 5 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0339] The resulting toner particles have an average particle diameterof 7.2 μm. A developer for developing an electrostatic latent image (19)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0340] Developer for Developing Electrostatic Latent Image (20)

[0341] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (9) 2,833 parts   (contact angle with water: 89°)Resin particle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion 125 parts Lauroyl peroxide  12 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0342] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 49° C. under stirring.After maintaining at 49° C. for 2 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.0 μm are formed. After further maintaining at 49° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 4.2 μmare formed.

[0343] (Coalescing Step)

[0344] The aggregated particle dispersion has pH of 2.5. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 5.5, and the mixture is then heated to 75°C. under continuous stirring, followed by maintaining for 4 hours.Thereafter, the reaction product is filtered and sufficiently washedwith ion exchanged water, followed by drying by using a vacuum dryer, soas to obtain toner particles.

[0345] The resulting toner particles have an average particle diameterof 4.3 μm. A developer for developing an electrostatic latent image (20)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0346] Developer for Developing Electrostatic Latent Image (21)

[0347] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (10) 2,400 parts   (contact angle with water: 86°)Resin particle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion  63 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0348] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 85° C. under stirring.After maintaining at 85° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 5.3 μm are formed. After further maintaining at 85° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.5 μmare formed.

[0349] (Coalescing Step)

[0350] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 7.2, and the mixture is then heated to 95° C. undercontinuous stirring, followed by maintaining for 5 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0351] The resulting toner particles have an average particle diameterof 5.7 μm. A developer for developing an electrostatic latent image (21)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0352] Developer for Developing Electrostatic Latent Image (22)

[0353] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (11) 2,400 parts   (contact angle with water: 89°)Resin particle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion  63 parts Lauroyl peroxide  10 parts Aluminum sulfate  5parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 100 parts

[0354] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 64° C. under stirring.After maintaining at 64° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 5.0 μm are formed. After further maintaining at 65° C.for 3 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.3 μmare formed.

[0355] (Coalescing Step)

[0356] The aggregated particle dispersion has pH of 2.4. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 6.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 5 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0357] The resulting toner particles have an average particle diameterof 5.4 μm. A developer for developing an electrostatic latent image (22)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0358] Developer for Developing Electrostatic Latent Image (23)

[0359] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (12) 900 parts (contact angle with water: 82°) Resinparticle dispersion (14) 225 parts (contact angle with water: 78°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion  63 parts Aluminum sulfate  5 parts (produced by Wako PureChemical Industries, Ltd.) Ion exchanged water 1,000 parts  

[0360] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 64° C. under stirring.After maintaining at 61° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 5.0 μm are formed. After further maintaining at 61° C.for 4 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.4 μmare formed.

[0361] (Coalescing Step)

[0362] The aggregated particle dispersion has pH of 2.5. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 7.2, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 6 hours.Thereafter, the reaction product is filtered and sufficiently washedwith ion exchanged water, followed by drying by using a vacuum dryer, soas to obtain toner particles.

[0363] The resulting toner particles have an average particle diameterof 5.5 μm. A developer for developing an electrostatic latent image (23)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0364] Developer for Developing Electrostatic Latent Image (24)

[0365] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 2,850 parts   (contact angle with water: 88°)Resin particle dispersion (13) 150 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion  63 parts Lauroyl peroxide  12 parts Aluminum sulfate  7parts (produced by Wako Pure Chemical Industries, Ltd.) Ion exchangedwater 150 parts

[0366] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 63° C. under stirring.After maintaining at 63° C. for 2 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.6 μm are formed. After further maintaining at 63° C.for 3 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 4.8 μmare formed.

[0367] (Coalescing Step)

[0368] The aggregated particle dispersion has pH of 2.7. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 5.3, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 6 hours.Thereafter, the reaction product is filtered and sufficiently washedwith ion exchanged water, followed by drying by using a vacuum dryer, soas to obtain toner particles.

[0369] The resulting toner particles have an average particle diameterof 4.8 μm. A developer for developing an electrostatic latent image (24)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0370] Developer for Developing Electrostatic Latent Image (25)

[0371] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 1,650 parts (contact angle with water: 88°)Resin particle dispersion (13) 1,350 parts (contact angle with water:79°) Colorant particle dispersion (1) 100 parts Releasing agent particledispersion 63 parts Lauroyl peroxide 7 parts Aluminum sulfate 7 parts(produced by Wako Pure Chemical Industries, Ltd.) Ion exchanged water120 parts

[0372] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.1 μm are formed. After further maintaining at 65° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 4.3 μmare formed.

[0373] (Coalescing Step)

[0374] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium hydrogencarbonate (produced by WakoPure Chemical Industries, Ltd.) to 0.5% by weight is gradually addedthereto to adjust the pH to 5.2, and the mixture is then heated to 90°C. under continuous stirring, followed by maintaining for 4 hours.Thereafter, the reaction product is filtered and sufficiently washedwith ion exchanged water, followed by drying by using a vacuum dryer, soas to obtain toner particles.

[0375] The resulting toner particles have an average particle diameterof 4.4 μm. A developer for developing an electrostatic latent image (25)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0376] Developer for Developing Electrostatic Latent Image (26)

[0377] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 2,347 parts (contact angle with water: 88°)Resin particle dispersion (13) 587 parts (contact angle with water: 79°)Colorant particle dispersion (3) 117 parts Releasing agent particledispersion 63 parts Lauroyl peroxide 10 parts Aluminum sulfate 5 parts(produced by Wako Pure Chemical Industries, Ltd.) Ion exchanged water100 parts

[0378] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.1. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 68° C. under stirring.After maintaining at 68° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.8 μm are formed. After further maintaining at 68° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.0 μmare formed.

[0379] (Coalescing Step)

[0380] The aggregated particle dispersion has pH of 2.6. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.9, and the mixture is then heated to 85° C. undercontinuous stirring, followed by maintaining for 3 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0381] The resulting toner particles have an average particle diameterof 5.2 μm. A developer for developing an electrostatic latent image (26)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0382] Developer for Developing Electrostatic Latent Image (27)

[0383] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 2,267 parts (contact angle with water: 88°)Resin particle dispersion (13) 567 parts (contact angle with water: 79°)Colorant particle dispersion (2) 250 parts Releasing agent particledispersion 63 parts Aluminum sulfate 5 parts (produced by Wako PureChemical Industries, Ltd.) Ion exchanged water 100 parts

[0384] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.1. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 68° C. under stirring.After maintaining at 68° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.9 μm are formed. After further maintaining at 68° C.for 3 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.3 μmare formed.

[0385] (Coalescing Step)

[0386] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.5, and the mixture is then heated to 85° C. undercontinuous stirring, followed by maintaining for 3 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0387] The resulting toner particles have an average particle diameterof 5.2 μm. A developer for developing an electrostatic latent image (27)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0388] Developer for Developing Electrostatic Latent Image (28)

[0389] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 2,400 parts (contact angle with water: 88°)Resin particle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (4) 109 parts Releasing agent particledispersion 63 parts Lauroyl peroxide 10 parts Aluminum sulfate 5 parts(produced by Wako Pure Chemical Industries, Ltd.) Ion exchanged water100 parts

[0390] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 68° C. for 2 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.9 μm are formed. After further maintaining at 65° C.for 3 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.3 μmare formed.

[0391] (Coalescing Step)

[0392] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.6, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0393] The resulting toner particles have an average particle diameterof 5.5 μm. A developer for developing an electrostatic latent image (28)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0394] Developer for Developing Electrostatic Latent Image (29)

[0395] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 2,400 parts (contact angle with water: 88°)Resin particle dispersion (14) 225 parts (contact angle with water: 78°)Colorant particle dispersion (1) 109 parts Releasing agent particledispersion 65 parts Lauroyl peroxide 10 parts Aluminum sulfate 5 parts(produced by Wako Pure Chemical Industries, Ltd.) Ion exchanged water100 parts

[0396] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 66° C. under stirring.After maintaining at 65° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 4.3 μm are formed. After further maintaining at 65° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 4.5 μmare formed.

[0397] (Coalescing Step)

[0398] The aggregated particle dispersion has pH of 2.6. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.9, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0399] The resulting toner particles have an average particle diameterof 4.8 μm. A developer for developing an electrostatic latent image (29)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0400] Developer for Developing Electrostatic Latent Image (30)

[0401] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (12) 900 parts (contact angle with water: 82°) Resinparticle dispersion (13) 600 parts (contact angle with water: 79°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion 63 parts Lauroyl peroxide 10 parts Aluminum sulfate 5 parts(produced by Wako Pure Chemical Industries, Ltd.) Ion exchanged water100 parts

[0402] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 3 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 5.3 μm are formed. After further maintaining at 65° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.6 μmare formed.

[0403] (Coalescing Step)

[0404] The aggregated particle dispersion has pH of 2.3. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 5.0, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0405] The resulting toner particles have an average particle diameterof 5.7 μm. A developer for developing an electrostatic latent image (30)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

[0406] Developer for Developing Electrostatic Latent Image (31)

[0407] (Aggregation Step) Preparation of Aggregated Particles Resinparticle dispersion (7) 3,000 parts (contact angle with water: 88°)Colorant particle dispersion (1) 100 parts Releasing agent particledispersion 63 parts Lauroyl peroxide 10 parts Aluminum sulfate 5 parts(produced by Wako Pure Chemical Industries, Ltd.) Ion exchanged water100 parts

[0408] The foregoing components are placed in a round flask made ofstainless steel and adjusted to pH 2.0. The contents of the flask aredispersed by using a homogenizer (Ultra-Turrax T50, produced by IKACorp.) and heated over an oil bath for heating to 65° C. under stirring.After maintaining at 65° C. for 2 hours, the observation by an opticalmicroscope confirms that aggregated particles having an average particlediameter of about 5.1 μm are formed. After further maintaining at 65° C.for 2 hours, the observation by an optical microscope confirms thataggregated particles having an average particle diameter of about 5.3 μmare formed.

[0409] (Coalescing Step)

[0410] The aggregated particle dispersion has pH of 2.2. An aqueoussolution obtained by diluting sodium carbonate (produced by Wako PureChemical Industries, Ltd.) to 0.5% by weight is gradually added theretoto adjust the pH to 4.5, and the mixture is then heated to 90° C. undercontinuous stirring, followed by maintaining for 4 hours. Thereafter,the reaction product is filtered and sufficiently washed with ionexchanged water, followed by drying by using a vacuum dryer, so as toobtain toner particles.

[0411] The resulting toner particles have an average particle diameterof 5.5 μm. A developer for developing an electrostatic latent image (31)is produced by using the resulting toner particles in the same manner asin the developer for developing an electrostatic latent image (18).

EXAMPLE 17

[0412] A modified machine of a color duplicator, Acolor 930, produced byFuji Xerox Co., Ltd. is prepared in the following manner. The releasingoil supplying unit of the duplicator is detached, and a fixing unitcontaining a fixing roll and a pressure roll, which are covered withfilms of a ethylene-vinylidene fluoride-tetrafluoroethylene copolymer onthe surfaces thereof, is installed. The developer for developing anelectrostatic latent image (18) is installed in a developer of themodified duplicator, and a non-fixed image is prepared to have a solidpart and a thin line part. The non-fixed image is fixed in such a mannerthat the rotation speed of the roll is adjusted to make the contact timeof the fixing roll and the non-fixed image be 0.04 second, with thesurface temperature of the fixing roll varying from 60 to 200° C. at aninterval of 5° C. The fixed image is folded inside at the substantialcenter of the solid part of the fixed image to evaluate the breakage ofthe fixed image, and the fixing temperature where no problem occurs isdesignated as the lowest fixing temperature. Reproducibility of the thinlines, background fogging and hot offset are evaluated with the nakedeye. Furthermore, the toner used is evaluated for the characteristics,the particle size, the particle size distribution and the fixingcharacteristics. The results are shown in Tables 3 and 4 below.

[0413] In the tables, Tm represents the melting point of the toner,GL(30) represents the storage elastic modulus at 30° C.; GL(Tm) andGL(Tm+10) represent the storage elastic modulus at the melting point andthat at a temperature higher by 10° C. than the melting point,respectively; GN(Tm) and GN(Tm+10) represent the loss elastic modulus atthe melting point and that at a temperature higher by 10° C. than themelting point, respectively; Δlog GL represents |log GL(Tm+20)−logGL(Tm+50)|; and Δlog GN represents |log GN(Tm+20)−log GN(Tm+50)|.

EXAMPLES 18 TO 29 Comparative Examples 4

[0414] Evaluation is conducted in the same manner as in Example 17except that the developers for developing an electrostatic latent image(19) to (31) are used instead of the developer for developing anelectrostatic latent image (18). The results are shown in Tables 3 and4. TABLE 3 Tm GL(30) × GL(Tm) × GL(Tm + 10) × GN(Tm) × GN(Tm + 10) ×Developer (’ C.) 10⁵ 10⁵ 10³ 10⁵ 10³ Δlog GL Δlog GN Example 17 18 693.2 2.8 4.2 4.0 4.6 1.2 1.2 Example 18 19 85 5.9 6.6 6.2 7.0 5.2 1.2 1.3Example 19 20 60 1.5 1.2 9.2 3.1 8.2 1.1 1.0 Example 20 21 81 4.8 4.02.2 6.5 2.5 0.2 0.4 Example 21 22 67 8.0 7.6 1.5 9.3 1.3 0.7 0.5 Example22 23 60 3.5 3.4 8.3 3.9 8.0 0.3 0.4 Example 23 24 71 3.2 2.8 5.2 4.18.5 1.1 1.3 Example 24 25 66 3.2 2.8 4.8 4.0 4.5 1.0 1.0 Example 25 2669 3.2 2.8 5.0 4.3 4.5 0.8 0.7 Example 26 27 69 3.2 2.8 4.9 4.2 5.1 1.21.1 Example 27 28 69 3.2 2.8 4.6 4.3 4.6 0.8 0.5 Example 28 29 69 3.22.8 3.8 4.2 1.6 0.9 0.5 Example 29 30 61 3.2 2.8 5.2 4.2 4.0 1.1 1.5Comparative 31 72 3.1 2.6 3.2 4.6 1.2 1.3 1.0 Example 4

[0415] TABLE 4 Average Fixing Reproduci- diameter temperature bility ofBackground Developer (μm) GSDv Tan δ (° C.) thin lines fogging Hotoffset Example 17 18 5.3 1.21 0.91 85 good none no occurrence Example 1819 7.2 1.20 1.19 100  good none no occurrence Example 19 20 4.3 1.241.12 75 good none no occurrence Example 20 21 5.7 1.22 0.88 95 good noneno occurrence Example 21 22 5.4 1.22 1.15 80 good none no occurrenceExample 22 23 5.5 1.23 1.04 80 good none no occurrence Example 23 24 4.81.20 0.63 85 good none no occurrence Example 24 25 4.4 1.22 1.07 90 goodnone no occurrence Example 25 26 5.2 1.20 1.11 85 good none nooccurrence Example 26 27 5.2 1.25 0.96 85 good none no occurrenceExample 27 28 5.5 1.25 1.00 85 good none no occurrence Example 28 29 4.81.25 2.38 85 good none no occurrence Example 29 30 5.7 1.24 1.30 85 goodnone no occurrence Comparative 31 5.5 1.38 2.67 85 slightly poor slightno Example 4 occurrence occurrence

[0416] It is understood from Tables 3 and 4 that when the developers fordeveloping an electrostatic latent image containing the toners fordeveloping an electrostatic latent image in Examples 17 to 29 are used,in comparison to the developer for developing an electrostatic latentimage containing the toner for developing an electrostatic latent imagein Comparative Example 4, the particle size distribution becomes narrow,i.e., the particle diameters of the respective particles of the tonercan be uniformized, and therefore the toners are excellent inreproducibility of thin lines, cause no background fogging, and areexcellent in low temperature fixing property. Furthermore, it is alsounderstood that the toners are excellent in image stability upon highspeed fixing particularly in the case where a color toner is used.

[0417] Owing to the foregoing constitution, the invention can provide atoner for developing an electrostatic latent image having excellent lowtemperature fixing property and containing a colorant and a releasingagent uniformly dispersed. The invention can provide a toner fordeveloping an electrostatic latent image and a process for producing thesame, as well as a developer for developing an electrostatic latentimage and a process for forming an image using the same, which toner isproduced by a simple production process, has good reproducibilityparticularly in particle size and particle size distribution, isexcellent in production stability, has a wide fixing region, and isexcellent in low temperature fixing property. The invention can providea toner for developing an electrostatic latent image and a process forproducing the same, as well as a developer for developing anelectrostatic latent image and a process for forming an image using thesame, which toner is excellent in production stability and storagestability of resin particles formed by the aggregation process, and isexcellent in charging property, particularly environmental stability andtime-lapse stability, whereby an excellent image can be formed even by amachine using a belt type fixing unit or a high speed fixing unit, whichhave a low heating ability upon fixing.

[0418] The entire disclosure of Japanese Patent Applications No.2000-260311 filed on Aug. 30, 2000 including specification, claims,drawings and abstract and No. 2000-303912 filed on Oct. 3, 2000including specification, claims and abstract is incorporated herein byreference in its entirety.

What is claimed is:
 1. A toner for developing an electrostatic latentimage comprising: a crystalline resin having a melting point as a binderresin; and at least one compound which is selected from A) an estercompound having an alkyl group having from 6 to 32 carbon atoms and B) aresin having a contact angle with water that is smaller than that of thecrystalline resin.
 2. The toner for developing an electrostatic latentimage as claimed in claim 1, wherein the toner satisfies the followingproperty: when the temperature is changed within a temperature range ofabout from 40 to 110° C., values of a storage elastic modulus and a losselastic modulus have an area which is changed by 10² or more per atemperature difference of 10° C.
 3. The toner for developing anelectrostatic latent image as claimed in claim 1, wherein the toner hasa storage elastic modulus at 30° C. at an angular frequency of 1 rad/secof about 1×10⁵ Pa or more.
 4. The toner for developing an electrostaticlatent image as claimed in claim 1, wherein the toner further comprisesa releasing agent.
 5. The toner for developing an electrostatic latentimage as claimed in claim 1, wherein the ester compound has a molecularweight of about from 200 to 1,500.
 6. The toner for developing anelectrostatic latent image as claimed in claim 1, wherein thecrystalline resin is a polymerized monomer which contains a sulfonylgroup-containing monomer.
 7. The toner for developing an electrostaticlatent image as claimed in claim 1, wherein the toner satisfies thefollowing equation (1): 0≦|log GL(Tm+20)−log GL(Tm+50)|≦1.5  (1) whereinTm represents a melting point of the toner, GL(Tm+20) represents astorage elastic modulus at Tm+20° C., and GL(Tm+50) represents a storageelastic modulus at Tm+50° C., and the following equation (2): 0≦|logGN(Tm+20)−log GN(Tm+50)|≦1.5  (2) wherein GN(Tm+20) represents a losselastic modulus at Tm+20° C., and GN(Tm+50) represents a loss elasticmodulus at Tm+50° C.
 8. The toner for developing an electrostatic latentimage as claimed in claim 1, wherein the toner has a loss tangent tan δat Tm+20° C., where Tm represents a melting point of the toner,satisfying 0.01≦tan δ≦2 at an angular frequency of 1 rad/sec.
 9. Thetoner for developing an electrostatic latent image as claimed in claim1, wherein the resin has a contact angle with water that is smaller thanthat of the crystalline resin, the contact angle with water being aboutfrom 30 to 120°.
 10. The toner for developing an electrostatic latentimage as claimed in claim 1, wherein the resin has a contact angle withwater that is smaller than that of the crystalline resin by about 3° ormore.
 11. A process for producing a toner for developing anelectrostatic latent image comprising the steps of: mixing by agitatinga binder resin particle dispersion and an aggregated particle stabilizerdispersion to prepare an aggregated particle dispersion containing thebinder resin particles; and heating the aggregated particle dispersionto a temperature higher than a melting point of a crystalline resin toform toner particles.
 12. The process for producing a toner fordeveloping an electrostatic latent image as claimed in claim 11,comprising the steps of: mixing by agitating a binder resin particledispersion, a colorant particle dispersion and an aggregated particlestabilizer dispersion to prepare an aggregated particle dispersioncontaining the binder resin particles and the colorant particles; andheating the aggregated particle dispersion to a temperature higher thana melting point of a crystalline resin contained in the binder resin toform toner particles.
 13. The process for producing a toner fordeveloping an electrostatic latent image as claimed in claim 11, whereinthe aggregated particle stabilizer is an ester compound having an alkylgroup having from 6 to 32 carbon atoms or a resin having a contact anglewith water that is smaller than that of the crystalline resin.
 14. Aprocess for forming an image, comprising the steps of: forming anelectrostatic latent image; developing the electrostatic latent imagewith a developer to form a toner image; transferring the toner image toa fixing substrate; and fixing the toner image to the fixing substrate,wherein the toner for developing an electrostatic latent image asclaimed in claim 1 is used to form the toner image.
 15. The process forforming an image as claimed in claim 14, wherein in the fixing step, acontact time of a fixing member and an unfixed image on the fixingsubstrate is adjusted to a range of about from 0.01 to 0.05 second. 16.The process for forming an image as claimed in claim 14, wherein in thefixing step, a belt type fixing unit is used.